CA2344641A1

CA2344641A1 - Electrosurgical biopsy device and method

Info

Publication number: CA2344641A1
Application number: CA002344641A
Authority: CA
Inventors: Fred H. Burbank; Paul Lubock; Michael L. Jones; Richard L. Quick
Original assignee: Individual
Current assignee: SenoRx Inc
Priority date: 1998-09-23
Filing date: 1999-09-17
Publication date: 2000-03-30
Also published as: US6261241B1; US7625347B2; JP2002526191A; WO2000016697A2; US6689071B2; WO2000016697A3; AU5926699A; US20010014779A1; EP1115345A2; US20050090762A1

Abstract

An electrosurgical biopsy device includes a stylet and a cannula movably mounted on a base. The stylet has a shaft with a head at its distal end and a stylet ablation element extending distally from the head. The stylet shaft is disposed through the cannula for axial translation therein between withdrawn and extended positions. The cannula has an opening at its distal end and a cannula ablation element adjacent the opening. Both ablation elements are activatable with energy that ablates adjacent tissue. A translation mechanism controllably moves (a) the stylet between the withdrawn and extended positions and (b) the cannula between a proximal position and a distal position relative to the base. In use, with the stylet in the withdrawn position against the distal end of the cannula, and with the stylet ablation element activated, the stylet and the cannula are pushed through the skin and the underlying tissue until the stylet head is adjacent a targeted tissue mass. Next, the stylet is extended distally from the distal end of the cannula so that its head penetrates the tissue mass. The cannula ablation element is then activated, and the cannula is pushed through the tissue mass toward the stylet head, thereby cutting a "core" through the tissue mass that is captured as a tissue specimen within the distal end of the cannula. The cannula and the stylet are then removed from the patient's body.

Description

WO 00116697 PCTlUS99/21416 4 Not Applicalble 7 Not Applicable The present invention relates to devices and methods for removing a 11 sample of tissue from a human or animal. In particular, the present invention 12 pertains to devices and methods for conducting a biopsy to remove a sample or 13 specimen of a tumor or lesion for examination and analysis.
14 In diagnosing and treating certain medical conditions, such as potentially cancerous tumors, it may be desirable to extract from a portion of 16 suspicious tissue, such as a tumor, a specimen of the suspicious tissue for 17 detailed examination and analysis. The process of removing such a specimen 18 of tissue is referred to as a biopsy.
19 In many instances, the suspicious tissue to be examined is inside the patient's body. For example, the suspicious tissue may be a tumor inside a 21 human breast. To minimize surgical intrusion into the body, it is desirable to 22 be able to insert a small instrument into the body for extracting a portion of the 23 suspicious tissue.
24 Different types of instruments and procedures have been developed for conducting biopsies to extract a tissue specimen for analysis. One device that 26 has been developed is the fine needle aspirator. This device comprises a 27 hollow needle, the end of which is sharpenedl. The needle is inserted into the 28 suspicious tissue so that individual cells or clusters of cells of the tissue lodge 1 inside the hollow core of the needle. The needle is then extracted from the 2 patient, and the cells and fluid removed from the needle for a cytological 3 examination. In certain circumstances, hovc~ever, it may be desirable to extract 4 portions of tissue for a histological examinaation, a procedure that is not typically feasible using a fine needle aspirator.
6 Another type of tissue-sampling device for biopsies is exemplified by 7 the device described in U.S. Patent No. Re.:34,056 - Lindgren et al. This type 8 of device includes a forward stylet, which includes at its distal end a sharpened 9 cutting surface. The stylet may be, for example, a needle sized belzveen 12 and 20 gauge. Behind the sharpened cutting end of the stylet, along the shaft 11 thereof, is a groove. A hollow cannula surrounds the stylet, and has its distal 12 end sharpened to form a fine cutting edge. ,A mechanism is provided to move 13 the stylet and the cannula forward separately. For example, springs may be 14 used for this purpose. Preferably, the stylet and the cannula are moved forward rapidly so that the sharpened ends thereof may efficiently cut the 16 tissue. In operation, the operator of this type of device first causes the stylet to I7 be pushed forward through the tumor or suspect tissue. After the distal end of 18 the stylet has passed through the suspect tissue, a portion of the tissue 19 surrounding the stylet partially fills the groove on the shaft of the stylet. The cannula is then pushed forward so that the slharpened distal end of the cannula 21 cuts off the portion of the tissue that has filled the groove on the shaft of the 22 stylet, and encloses that tissue. The entire device may then be removed from 23 the patient's body, and the tissue trapped in l;he cannula removed for 24 examination and analysis.
U.S. Patent No. 5,526,822 - Burbank et al. discloses another type of 26 biopsy device that includes the ability to app>ly a vacuum to the groove in the 27 stylet. This vacuum assists in drawing tissue into the groove, ensuring that a 28 more substantial portion of tissue is severed by the cutting cannula. Using 1 such a system, it is in some cases possible to~ use. a relatively large stylet (e.g., 2 a 7 to 14 gauge needle) to obtain a relatively large tissue sample.
3 All of the above-described systems use knife edges to a cut the tissue.
4 The cutting edge must remain extremely sharp, so that it cuts the tissue cleanly. Moreover, the stylet and the cannula cutter must be propelled forward 6 rapidly to provide a clean cut through the tissue. Elaborate mechanisms are 7 typically employed to provide the rapid forward movement. Because the 8 knife edges move rapidly, however, there is :limited time for tissue to fill the .
9 groove on the stylet. Therefore, the system sometimes obtains a smaller sample than would be ideal. In addition, variations in tissue density and I 1 anatomy may cause the stylet to deflect ftom~ its ideal position in relation to the 12 tissue to be penetrated.
13 Electrosurgical techniques have been used in a variety of 14 circumstances, including certain types of biopsies. In electrosurgery, high frequency electrical energy is applied through a primary electrode to tissue.
16 The electrical energy flows through the tissue to a return electrode. The tissue 17 adjacent to the primary electrode is ablated, t;o form an opening in the tissue.
18 The return electrode in monopolar electrosurgery may be a large electrode 19 placed on the exterior of the patient's body at: a paint remote from the primary electrode. In bipolar electrosurgery, the return electrode may be a smaller 21 electrode positioned somewhat near the primary electrode. An exemplary 22 biopsy instrument using electrosurgical techxliques is described in International 23 Publication No. WO 98/08441.

SUMMARY OF THE INVENTION
26 The present invention, in one aspect, is a novel electrosurgical tissue 27 sampling device, or biopsy device, including a novel electrosurgical stylet. In 28 another aspect, the present invention is a method of using the novel biopsy 1 device to obtain a tissue specimen.
2 The novel stylet of the present invention includes a shaft that has a 3 proximal end and a distal end. At the distal a;nd of the stylet shaft is a 4 substantially hemispherical head. A stylet electrode extends distally from the stylet head. The stylet electrode may be activated with radio frequency (RF) 6 electrical energy to ablate the tissue adjacent the stylet electrode. A
cannula 7 that cooperates with the stylet also has a proximal end and a distal end. An 8 opening is formed at the distal end of the cannula. The distal end of the 9 cannula may be selectively separated from the stylet, or may abut the stylet to close the opening at the distal end of the canrlula. Also at the distal end of the 11 cannula is another electrode that also may be activated with radio-frequency 12 electrical energy to ablate the tissue adjacent the distal end of the cannula.
13 The system may be monopolar, in which the return electrical path is 14 provided by a return electrode attached to the. patient's body remote from the device. Alternatively, the system may be bipolar, in which the return electrical 16 path is provided by a return electrode on the device itself. The same return 17 electrical path may be used for both the elect~~ode on the stylet and the 18 electrode on the cannula.
19 In accordance with the method of the present invention, the electrode on the head of the stylet is energized. With the stylet in a withdrawn position 21 abutting against the distal end of the cannula, the stylet and the cannula are 22 pushed through the skin and the underlying tissue, while applying an RF
23 current, until the head of the stylet is adjacent a targeted tissue mass (e.g., a 24 lesion or tumor). Next, the stylet is extended distally from the distal end of the cannula so that its head penetrates the targeted tissue mass, whereby the stylet 26 head and the distal end of the cannula are on opposite sides of the tissue mass.
27 The electrode at the distal end of the cannula is then energized, and the 28 cannula is pushed through the tissue mass tovvard the stylet head, thereby - WO OO/ibb97 PCT/US99/21416 1 cutting a "core" through the tissue mass that is captured as a tissue specimen 2 within the distal end of the cannula. The carmula and the stylet are then 3 removed from the patient's body. After the cannula and the stylet have been 4 removed, they may be separated from one ar.~other, and the tissue specimen S enclosed within the cannula may be removed and examined.

? BRIEF DESCRIPTION OF 'T'HE DRAWINGS
8 Figure 1 is a perspective view of a preferred embodiment of a biopsy 9 device constructed in accordance with the present invention;
Figure 1 A is a perspective view of a portion of the cannula and stylet of 11 a modified form of the preferred embodiment of the biopsy device;
12 Figure 2 is a distal end view of the device illustrated in Figure 1, taken 13 from the left side of Figure l;
14 Figure 3 is a perspective view, partially broken away, of a preferred embodiment of an electrosurgical stylet constructed in accordance with an 16 aspect of the present invention, and incorporated in the device illustrated in 17 Figure 1;
18 Figure 4 is a top view of the device of Figure 1, with the device set to 19 begin a biopsy procedure in accordance with the method of the present invention;
21 Figure S is a second top view, similar to the view of Figure 4, of the 22 device of Figure 1, with the stylet extended fir an intermediate step of a 23 biopsy procedure in accordance with the metlhod of the present invention;
24 Figure 6 is a third top view, similar to the view of Figure 4, of the device of Figure 1, with both the stylet and tl:~e cannula extended for a further 26 stage of a biopsy procedure in accordance with the method of the present 27 invention;
28 Figure 7 is a cross-sectional view taken along line 7- 7 of Figure 6;

- 1 Figure 8 is a cross-sectional view taken along line 8 - 8 of Figure 6;
2 Figure 9 is a staggered cross-sectional view taken along line 9 - 9 of 3 Figure 4;
4 Figure 10 is a cross-sectional view tal;en along line 10 - 10 of Figure 9;
Figure 11 is a cross-sectional view tal;en along line 11 - 11 of Figure 6 10;
Figure 12 is a cross-sectional view of the cannula and stylet, taken 8 along line 12 - 12 of Figure 6;
9 Figure 13 is a view taken along line 1:3-- 13 of Figure S, showing a distal end view of the cannula, and a cross-sE;ctional view of the styles shaft;
I I Figure 14 is a cross-sectional view tal~:en along Iine 12 14 - 14 of Figure 12;
13 Figure 15 is a cross-sectional view of the base of the biopsy device, 14 taken along line I S - 15 of Figure 7;
Figure 16 is a side elevational view of an alternative embodiment of the 16 electrosurgical stylet that may be incorporated in the biopsy device of the 17 present invention;
18 Figure 17 is a perspective view of an alternative embodiment of the 19 cannula portion of the biopsy device of the present invention;
Figure 18 illustrates the step of inserting the biopsy device into tissue 21 for extracting a tissue specimen, in accordance with the method of the present 22 invention;
23 Figure 19 illustrates the biopsy device positioned to begin extracting a 24 tissue specimen in accordance with the method of the present invention;
Figure 20 illustrates the biopsy device at an intermediate step of the 26 biopsy procedure in accordance with the method of the present invention;
and 27 Figure 21 illustrates the biopsy device at a later intermediate step of the 28 biopsy procedure in accordance with the method of the present invention.

WO 00/16697 PCTlUS99/21416 2 DETAILED DESCRIPTION O~F THE INVENTION
3 Referring first to Figure 1, a particular preferred embodiment of a 4 biopsy device 100, constructed in accordance with the present invention; is illustrated. The biopsy device 100 includes <~ probe 102, a base unit 104, an 6 energy source, such as a radio-frequency generator 106, and a control unit 108.

8 The probe 102 includes a stylet 110 and a cannula 112. The stylet 110 electrosurgically separates tissue through the use of an electrical current activated at high frequency, such as a frequency in the radio frequency range.
11 The stylet 110, when electrically activated, ablates tissue adjacent its 12 electrically active components.
13 The stylet 110, comprising an aspect of the present invention, is shown 14 in Figure 3. The stylet 110 includes a stylet lhead I22 having a substantially cylindrical body with a substantially hemispherical surface at the distal end of 16 the stylet head 122. The stylet head I22 is fc>rmed of an electrically insulating 17 material, such as a plastic. The stylet head I;Z2 is attached to the distal end of 18 a stylet shaft 124, which is also formed of an electrically insulating material.
19 The stylet shaft 124 may have a central longitudinal bore through it, preferably along the longitudinal axis of the shaft 124.
21 A conductive metal stylet electrode 126 protrudes distally from the 22 stylet head 122. In the illustrated embodiment, the stylet electrode 126 is 23 formed of an arcuate length of electrical conductor that protrudes from 24 diametrically opposite sides of the stylet head 122, and extends over the hemispherical distal end surface of the stylet head 122. The radius of Zb curvature for the stylet electrode 126 is substantially coplanar with the 27 longitudinal axis of the stylet shaft I24. The stylet electrode 126 forms a first 28 tissue ablation element for electrosurgically separating tissue so as to create an WO 00/16697 PCTlUS99/21416 1 incision.
2 For the purposes of the present description of the invention, the term 3 "ablation", as used in this specification, is de;f ned as the process of creating an 4 incision by vaporizing tissue. The preferred embodiment described herein uses electrical energy in the radio frequency range for the ablation process.
6 However, tissue ablation may also be accomplished with other energy sources, 7 such as microwaves or ultrasound. In such cases, the configuration of the 8 ablation elements rnay differ from the ablation electrodes described 9 hereinbelow. The energy supply and control system may differ as well. The appropriate variations and modifications in these components to accommodate I 1 the alternative energy sources will suggest themselves to those skilled in the I2 pertinent arts.
13 The stylet electrode 126 merges into a single stylet electrical conductor 14 128 inside the stylet head 122. The single stylet electrical conductor 128 extends through the central bore in the stylet shaft 124. The stylet conductor 16 128 is electrically connected with both ends ~of the stylet electrode 126.
17 An alternative embodiment of the styl.et head is illustrated in Figure 16.
18 The embodiment illustrated in Figure 16 includes a conical head 130 that has I9 an electrically conductive apex portion 132 that forms the styles electrode.
The apex portion is secured to the distal end of an insulative, frustrum-shaped 21 base portion 134. The conical stylet electrode 132, which forms the stylet 22 tissue ablation element, is in electrical contact with the stylet conductor 23 (as described above with reference to Figure 3).
24 The cannula I IZ is formed of an elonl;ated hollow outer tube 140 (Figures 12, 13, and I4) that has a distal end and a proximal end. Preferably, 26 the longitudinal axis of the cannula I 12 coincides with the longitudinal axis of 27 the stylet shaft 124. The outer tube 140 of th.e cannula 112 is formed of an 28 electrically nonconductive or insulating material, such as plastic, and may be WO 00/16697 PCT/US991214t6 - 1 formed by extrusion. For example, the outer tube 140 of the cannula may be 2 formed of a polyimide. The outer surface of the cannula tube 140 may be 3 coated with TEFLON~ (polytetrafluoroethylene) or similar low-friction 4 polymeric material to reduce sticking between the surface and the surrounding tissue.
6 At the distal end of the cannula 112 is. a cannula electrode 142 forming 7 a second tissue ablation element. The cannula electrode 142 may be formed of 8 the distal end of a tubular conductor 144 extE;nding along the length of the 9 cannula 112, inside the outer tube 140.
i0 An electrically insulating inner sleeve 146 may cover the inner surface 11 of the tubular conductor 144. The inner cannula sleeve 146 may also be 12 formed by extrusion of a polyimide. The inner surface of the inner cannula I3 sleeve 146 may be coated with a low-friction polymeric material, such as 14 TEFLON~. The inner insulating sleeve 146 is spaced from the stylet shaft 124 to form an annular passage 148 that is open at the distal end of the cannula 16 112. The annular passage 148 receives tissue: samples that are severed by the 17 cannula electrode 142, as described below.
18 In a bipolar configuration for the probe, described below, the cannula 19 112 will include other elements 152, 156, shown in Figures 12, 13, and 14.
These other elements, described below, are not incorporated in the monopolar 21 configuration.
22 The stylet 110 and the cannula 112 may be moved relative one another 23 along their common longitudinal axis. For e:Kample, the stylet 110 may be 24 moved relative to the cannula 112 between an extended position in which the distal end of the stylet shaft 124 and the style;t head 122 are separated from the 26 distal end of the cannula 112, and a withdra~m position in which the stylet 27 head 122 abuts or is in close proximity to the distal end of the cannula 112.
28 Those familiar with electrosurgical techniques will understand that WO O~116697 PCT/US99/21416 1 when a high frequency electrical current is applied to a primary electrode, such 2 as the stylet electrode 126, and the primary electrode is exposed to tissue, the 3 tissue adjacent the primary electrode is ablated. To perform such 4 electrosurgery, a return electrical path through the tissue is required, to close 5 the electrical circuit.

6 An electrosurgical device may be either monopolar or bipolar. With a 7 monopolar device, the return electrical path is provided through a return 8 electrode that may be a grounded contact pad that is applied to the exterior of 9 the patient's body at a point remote from where the primary electrode is placed 10 in the body. With a. bipolar device, the return electrical path is provided from 11 the primary or ablation electrode through a reaurn electrode that is located 12 relatively near the primary electrode. The bipolar return electrode is contained 13 on the same instrument body as the primary electrode. Although parts of the 14 present invention are described with reference to a monopolar canfiguration, I S and parts are described with reference to a bipolar configuration, those skilled 16 in the art will recognize how the device may be implemented in either 17 configuration.
i 8 In the monopolar configuration of the biopsy device illustrated in 19 Figure l, a patient return pad 150 is attached to the patient's body, and is in electrical contact with the RF generator 106. The patient return pad 150 forms 21 a return electrode for the energy delivered by the RF generator 106 to the 22 stylet electrode 126 and the cannula electrodf; 142. In the monopolar 23 configuration, the annular conductor 144 that: terminates in the cannula 24 electrode 142 is disposed between the extern<~.i insulating layer of the tube 140, and the inner insulating sleeve 146.
26 A probe 102' used in the bipolar confi~,~uration of the biopsy device in 27 accordance with the present invention is shown in Figure 1 A. In the bipolar 28 configuration, the return electrical path is provided through a conductor 1 contained within a bipolar cannula 112'. Referring to Figures I2, 13, 14, and 2 l A, the addirional elements of the bipolar cannula 112' are shown. A
3 conductive layer 152 is contained just under the outer tube 140, and forms a 4 return path electrode. A pair of diametrically-opposed longitudinal side S openings, or slots 1 S4 (one of which is shown in Figure lA) are provided in the 6 outer tube 140. These side openings 1 S4 may extend longitudinally along a 7 substantial portion of the length of the cannu.la 112'. Through these openings 8 I S4 in the outer tube 140, the conductive layer 1 S2 forming the return path 9 electrode is exposed to the environment surrounding the cannula I I2'. Thus, when the probe 102' (Figure 1 A) is inserted into a patient's tissue, the return l 1 electrode 140 is in contact with the tissue, and electrical current may flow 12 through the tissue from the stylet electrode I26 and the cannula electrode 13 to the return electrode I S2. The return electrode is advantageously 14 electrically connected to ground potential.
1S Referring now particularly to Figure 1.2, the annular cannula conductor 16 144 in a bipolar implementation is spaced from the return path electrode 1 17 by an insulating layer l S6 of non-conductive material, such as plastic.
The 18 insulating layer I S6 electrically isolates the return path electrode 1 S2 from the 19 cannula conductor 144.
When activated with a current oscillating at high frequency (such as in 21 the radio frequency range), the cannula electrode 142 ablates tissue adjacent to 22 the cannula electrode. As with the stylet electrode 126, the operation may be 23 either monopolar or bipolar. For operation in accordance with a bipolar 24 technique, the same return electrode 1 S2 used with the stylet electrode 2S may also be used in conjunction with the cannula electrode 142. However, 26 those skilled in the art, taking the teaching provided herein, will also recognize 27 that alternative electrical return paths may be: provided.
28 An alternative embodiment of the cannula is illustrated in Figure 17.

WO OO/ibb97 PCTNS99/2141b 1 This particular alternative embodiment is illustrated as a rrionopolar device.
2 However, those skilled in the art will recogni~:ze that the illustrated embodiment 3 may be modified to add a return electrode to implement a bipolar embodiment.
4 In the alternative embodiment illustrated in Figure 17, the cannula is formed of a cannula body 160.. A cannula conduit 162 extends along the length of the 6 cannula body 160. A length of conductor e~saends through the cannuia conduit 7 162, and is formed into a substantially circular cannula electrode 164 that 8 coincides with the distal end of the cannula body 160. Those skilled in the art 9 will readily recognize that other configurations may be used to form the cannula electrode at the distal end of the cannula. For example, the cannula 11 conduit 162 may be formed as a groove cut along the length of the cannula 12 body 160. Similarly, the cannula conduit 16;? may be formed on the interior 13 surface of the cannula body 160.
14 An energy source, such as the radio-frequency generator 106, generates the electrical current required for application to the stylet electrode 126 and the 16 cannula electrode 142. The design, construction, and operation of such a 17 generator and control unit are conventional and well-understood by those 18 familiar with electrosurgery technology.
19 The base unit 104 controls the position and movement of the stylet 110, the cannula 112, and the application of the electrical energy generated by the 2I generator and control unit 106 to the stylet electrode 126 and the cannula 22 electrode 142. The base unit 104 permits the cannula 1 I2 and stylet 110 to be 23 moved together, and also to be moved separately. For example, the probe 102, 24 including both the stylet I 10 and the cannula 112, may be moved between an extended position relative to the base unit 104 in which the distal end of the 26 stylet 110 and the distal end of the cannula l :f 2 are relatively farther from the 27 base unit 104, and a withdrawn position in which the distal end of the stylet 28 110 and the distal end of the cannula 112 are relatively closer to the base unit 1 104. Furthermore, the base unit 104 may extend the stylet 110 between an 2 extended position relative to the cannula 112,, and a withdrawn position 3 relative to the cannula 112.
4 The base unit 104 may be enclosed in a housing 202 (shown in phantom lines in Figure 1). The housing 202 protects the internal elements of 6 the device. The housing 202 may be substantially sealed to protect the internal 7 elements of the base unit 104 from contamination during use of the stylet 8 and cannula 112 during a biopsy procedure. :However, the housing 202 may 9 be selectively removable, or have an access panel (not shown) provided to allow access to certain elements within the base unit 104. In addition, the 11 housing 202 may be shaped to facilitate hand holding of the device, or it may 12 be configured to be attached to other devices (not shown) for holding the 13 biopsy device in the proper position for conducting the biopsy procedure.
14 Referring now to Figures 1, 4, 5, and 6, the base unit 104 includes a base 204 to which is fixed an electric motor 206 (preferably a DC motor 16 powered by a power supply 207). The motor 206 is employed for moving the 17 stylet 110 and the cannula 112 relative to the base unit 104. A cannula earner 18 210 is slidably mounted on the base 204. The; cannula 112 has a proximal end 19 that is attached to a cannula carrier 210. The cannula carrier 210 translates the cannula 112 longitudinally on the base unit 104. The stylet shaft 124 has a 21 proximal end that is attached to a stylet earner 220 that is slidably mounted on 22 the base 204. The styiet carrier 220 translate, the stylet 110 longitudinally on 23 the base 204. In combination with the cannula earner 210, the stylet carrier 24 220 also translates the stylet 110 relative to th,e cannula 112. The motor includes a drive shaft 221 to which is attached a drive screw 222. The drive 26 screw 222 is threaded through a screw-driven slide 224 that moves the cannula 27 carrier 210 and the stylet carrier 220 in the manner described below.
28 The stylet 110 and the cannula 112 are preferably separable from the _ WO 00/16697 PCT/US99/2t4t6 I stylet carrier 220 and the cannula carrier 210., respectively. In this way, the 2 entire probe unit .102; including the stylet 110 and cannula 112, may be 3 replaced upon each use, without having to replace the entire device. This 4 allows the stylet 110 and cannula 112 to be disposable, so that a new, sterile stylet and cannula may be used for each biopsy procedure.
6 The proximal end of the stylet 110 may be embedded in or attached to a 7 stylet foot 225, formed of an electrically insulating material, such as plastic.
8 The stylet foot 225 is removably mounted in the stylet carrier 220. For 9 example, the stylet foot 225 may fit into a correspondingly shaped recess in the stylet earner 220. A stylet retention strip 227, having its two ends 11 removably attached to the stylet earner 220, and extending across the top of 12 the stylet foot 225, retains the stylet foot 225 in the stylet carrier 220.
13 Similarly, the proximal end of the cannula 112 may be embedded in or 14 attached to a cannula foot 229, formed of an electrically insulating material, such as plastic. The cannula foot 229 is removably mounted in the cannula 16 carrier 210, such as by being retained in a coiTespondingly shaped recess in the 17 cannula carrier 210. A cannula retention strip 23I, having its two ends 18 removably attached to the cannula carrier 2 I t), and extending across the 19 cannula foot 229, retains the cannula foot 225> in the cannula carrier 210.
The entire probe unit 102; including the stylet 110 and the cannula 112 21 may be made available to medical doctors and hospitals as a single modular 22 unit, ready for attachment to the base unit 104. In this way, the sterility of the 23 probe unit 102 may be maintained. After completion of a biopsy procedure, 24 the entire probe unit 102 may then be removed from the base unit 104 and discarded in accordance with proper procedures for medical waste.
26 An exemplary mounting for the cannu:la carrier 210 on the base 204 is 27 illustrated in Figure 7. The base 204 include:. substantially U-shaped channels 28 226 along each side thereof. Horizontal extensions 228 of the bottom portion _ WO 4aJ/16697 PCT/US99/21416 - 1 of the cannula carrier 210 engage these channels 226. The mounting of the 2 cannula carrier 210 on the base 204 preferabl'~,y provides very little friction 3 between the cannula carrier 210 and the base 204. A low friction mounting 4 helps to ensure smooth and accurate movement of the cannula corner 210 5 relative to the base 204.
6 The mounting of the stylet carrier 220 on the base 204 is 7 advantageously similar to the mounting of the cannula carrier 210. An 8 exemplary mounting for the stylet carrier 22U on the base 204 is illustrated in 9 Figure 8. Horizontal extensions 230 of the bottom portion of the stylet corner 10 220 engage the U-shaped channels 226 formed in the base 204. The mounting 11 of the stylet carrier 220 on the base 204 preferably provides very little friction I2 between the stylet corner 220 and the base 204. A low friction mounting helps 13 to ensure smooth and accurate movement of tfhe stylet corner 220 relative to 14 the base 204.
I S The base 204 includes a plurality of stops that define the maximum 16 extent of the longitudinal movements of the c:annula carrier 210 and the stylet 17 carrier 220 along the base 204. In the particular embodiment illustrated, an 18 end piece 232 is provided at the distal end of the base 204. The end piece 19 forms a forward stop for the cannula carrier 2;10. An intermediate stop 234 is affixed to the base 204. The distal side of the; intermediate stop 234 forms a 21 rearward stop for the cannula carrier 210, while the proximal side of the 22 intermediate stop 234 forms a forward stop for the stylet carrier 220. A
back 23 stop 236 is affxed to the base 204 as a rearward stop fox the stylet carrier 220.
24 The cannula carrier 210 may be moved between a withdrawn position (illustrated in Figures 4 and 5) and an extended position (illustrated in Figure 26 6}. In the withdrawn position, the distal edge of the cannula carrier 210 is 27 spaced from the end piece 232 of the base 204, and the proximal edge of the 28 cannula carrier 210 abuts against the distal side of the intermediate stop 234.

WO 00/16697 PCT/US99/214t6 1 In this withdrawn position, the cannula I 12 is withdrawn relative to the base 2 204. When the cannula carrier 210 is in the extended position, the distal edge 3 of the cannula carrier 210 abuts against the end piece 232, and the cannula 4 is extended distally with respect to the base 2,04. As the cannula carnet moves toward the distal end of the base 204, the cannula 112 moves distally 6 with respect to the base 204. As the cannula carrier 210 moves toward the 7 proximal end of the base 204, the cannula 1 I:2 moves proximally with respect 8 to the base 204.
9 The stylet carnet 220 may also be moved between a withdrawn position (illustrated in Figure 4) and an extended position (illustrated in Figures 5 and 11 6). In the withdrawn position, the distal edge: of the stylet carrier 220 is spaced 12 from the intermediate stop 234, and the proximal edge of the stylet carrier 13 abuts against the back stop 236. In this withdrawn position, the stylet 110 is 14 withdrawn relative to the base 204. When the stylet carnet 220 is in the 1 S extended position, the distal edge of the stylet carrier 220 abuts against the 16 proximal side of the intermediate stop 234. As the stylet carrier 220 moves 17 longitudinally on the base 204 toward the distal end of the base, the stylet i 10 18 moves distally with respect to the base 204. ,As the stylet carrier 220 moves 19 longitudinally on the base 204 toward the proximal end of the base, the stylet 110 moves proximally with respect to the base 204.
21 A drive mechanism on the base 204 moves the cannula carrier 210 and 22 the stylet carrier 220. In the particular embodiment illustrated, the drive 23 mechanism includes the electric motor 206, the drive screw 222, arid the 24 screw-driven slide 224. The screw-driven slide 224 is slidably mounted on the base 204 so as to be movable between a proximal position in which it is 26 relatively near the motor 206, and a distal position in which the it is relatively 27 remote from the motor 206, and nearer the distal end of the base 204. The 28 movement of the screw-driven slide 224 controls the movement of the cannula _ WO 00116b97 PCT/US99/2I416 1 earner 210 and the stylet earner 220.
2 The screw-driven slide 224 is moved along the base 204 by the drive 3 screw 222, which in turn is driven by the motor 206 by means of the drive 4 shaft 22I . The motor 206 rotates the drive slr~aft 221 and the screw 222, the latter engaging threads (not shown) in the screw-driven slide 224 to move the 6 screw-driven slide 224 along the base 204. ~JVhen the motor 206 rotates in a 7 first direction (for example, clockwise), the motor turns the drive screw 222 in 8 the same direction, which in turn moves the screw-driven slide 224 from its 9 proximal position toward its distal position. When the motor 206 rotates in the opposite direction, the rotation of the screw :>.22 moves the screw-driven slide 11 224 in the opposite direction, toward its proximal position.
I2 A pair of push rods 240 are fixed to the distal side of the screw-driven I3 slide 224. Each of these push rods 240 extends through openings (not shown) 14 in the stylet carrier 220, so that the distal endls of the push rods 240 may engage the proximal side of the cannula carriier 210. A spring bias is provided 16 between the screw-driven slide 224 and the stylet carrier 220. This spring bias I7 tends to maintain a specific predetermined separation between the screw-I8 driven slide 224 and the stylet carrier 220. This spring bias may be provided 19 by a pair of coil springs 242, each of which surrounds one of the push rods 240.
21 The mechanical operation of the base unit 104 will now be described 22 with reference to Figures 4, 5, and 6. Referriing first to Figure 4, the biopsy 23 device is illustrated in a configuration in which it is set to begin a biopsy 24 procedure. The stylet 110 is withdrawn relative to the cannuia 112 so that the stylet 124 abuts against the distal end of the c;annula 112. The cannula 112 26 and stylet 110 are both withdrawn to the full extent possible relative to the 27 base 204; that is, they are at their respective proximal limits of travel relative 28 to the base 204.

WO 00/16b97 - PCT/US99/21416 1 As the motor 206 is operated, it turns the screw 222, which moves the 2 screw-driven slide 224 toward the distal end of the base 204 in the manner 3 described above. The springs 242 between tile screw-driven slide 224 and the 4 stylet carrier 220 maintain the predeterminedL spacing between the screw-s driven slide 224 and the stylet carrier 220, thus causing the stylet carrier 220 to 6 move toward the distal end of the base 204 avt approximately the same rate as 7 the screw-driven slide 224. However, the cannula carrier 210 remains in its 8 original position. Thus, the styiet 110 extends distally relative to the cannula 9 I I 2, so that the stylet head 122 separates from the distal end of the cannula 112. This continues until the distal ends of the push rods 240 contact the 11 proximal side of the cannula earner 210, as i'.llustrated in Figure S. At this 12 stage, the stylet head 122 is spaced from the .distal end of the cannula 112, 13 forming a gap between the proximal end of tl''ze stylet head I22 and the distal 14 end of the cannula 112.
Also at this stage, the distal side of the; stylet carrier 220 contacts the 16 proximal side of the intermediate stop 234, blocking further movement of 17 these stylet carrier 220 toward the distal end of the base 204. As the motor 18 206 continues to rotate the drive screw 222; it continues to move the screw-19 driven slide 224 toward the distal end of the hase 204. However, further movement of the stylet earner 220 is blockedl. As the spring bias provided by 21 the springs 242 is overcome, the springs 242 compress, and the screw-driven 22 slide 224 moves closer to the stylet carrier 22;0. As the screw-driven slide 224 23 moves closer to the stylet carrier 220, the push rods 240 extend from the distal 24 side of the stylet carrier 220 and engage the ~>roximal side of the cannula carrier 210. As the screw-driven slide 224 continues to move toward the distal 26 end of the base 204, the push rods 240 move the cannula carrier 210 toward 27 the distal end of the base 204. This forward (distal) movement of the cannula 28 carrier 210 moves the cannula 112 relative to~ the stylet 110, closing the gap WO OO/t6697 PCT/US99/21416 1 between the stylet head 122 and the distal end of the cannula 1 I2, so that the 2 stylet 110 is withdrawn relative to. the cannula 112.
3 When the distal end of the cannula I 1:2 contacts the proxiriial end of 4 stylet head 122 (as illustrated in Figure 6), further forward (distal) movement ,.
of the cannula carrier 210 should be stopped. Forward movement of the 6 cannula carrier 2I0 toward the distal end of the base 204 may be stopped by 7 stopping the motor 206. .The components of the device, including the base 8 and the stops 232, 234, 236, may also be dimensioned so that at that point the 9 distal side of the cannula carrier 210 contacts. the end piece 232 of the base to stop further movement of the cannula carrier 210 in the distal (forward) 11 direction.
12 As noted previously, the energy for the stylet electrode 126 and the 13 cannula electrode 142 is supplied by the RF generator 106. Furthermore, the 14 control of activation of the electrodes 126, 142; as well as control of the motor 206 that moves the cannular carrier 210 and the stylet carnet 220, is provided 16 by the control unit 108. Accordingly, electri~;,al paths must be provided to 17 conduct energizing current through the base unit 104 from the RF generator 18 106 to the stylet electrode 126 and the cannu:la electrode 142, and to conduct 19 control signals from the control unit 108 to the motor 206. (Control signals are also sent from the control unit 108 to the RF generator 106 to control the 21 activation of the electrodes I26; 142.) In addition, a return electrical path must 22 be provided for the patient return pad I50 (m~onopolar configuration) or the 23 return electrode 152 (bipolar configuration).
24 Referring now to Figure 15, the base .>.04 includes a plurality of electrical connectors 260a, 260b, 260c, 260d for providing electrical 26 connection to the RF generator 106 and the control unit 108, and to the power 27 supply 207 for the motor 206. A stylet lead 262, a cannula lead 264, and (in a 28 bipolar configuration only) a return lead 266 each have a first end that is 1 internally connected to separate ones of the connectors 260a-d. The other end 2 of the stylet lead 262 is connected to a stylet base contact 268 that is fixed with 3 respect to the base 204. For example, the stylet base contact 268 may be 4 embedded in the intermediate stop 234. Similarly, the other end of the cannula 5 lead 264 is connected to a cannula base contact 270 that is fixed with respect 6 to the base 204. Fox example, the cannula lead contact 264 may be embedded 7 in the base end piece 232.
8 The return lead 266 is included only in the bipolar configuration. -It is 9 not necessary in the monopolar configuration that includes the remote patient 10 return pad 150 (Figure I). In the monopolar configuration, the connection 11 between the patient return pad 150 and the RF generator and control unit 12 may be provided externally to the base unit 104. The return lead 266 in the 13 bipolar configuration may be connected to a cannula return base contact 272 14 that is fixed with respect to the base 204. For example, the return base contact 15 272 may also be embedded in the base end piece 232.

16 Referring next to Figure 9, the structure of the proximal ends of the 17 stylet 110 and the cannula 112, and the electrical paths for the stylet conductor 18 128 and for the cannula conductor 144, are illustrated. Referring f rst to the 19 electrical path for the stylet 110; the stylet base contact 268 is provided in the 20 intermediate stop 234. A stylet wire 274 provides an electrical current path 21 between the stylet base contact 268 and a styIet carrier contact 276 on the 22 stylet carrier 220. Because the position of th.e stylet carrier 220 changes with 23 respect to the intermediate stop 234, the styl<~t wire 2'74 should be able to 24 accommodate changes in the physical separation between the stylet carrier and the intermediate stop 234 while maintaining a connection between the 26 stylet base contact 268 and the stylet carrier contact 276. For example, the 27 stylet wire 274 may be a coiled wire wrapped around a longitudinal pin 278.
28 An opening 279 may be provided in the distal side of the stylet carrier 220 to - WO OOIlbb97 PCTIUS99121416 2i - 1 accommodate the coiled stylet wire 274. .
2 The stylet carrier contact 276 remains in contact with an extension 3 portion 280 of a stylet carrier terminal 282 that is mounted in the stylet foot 4 225. The stylet earner terminal 282, in turn, is in electrical contact with the stylet electrical conductor 128 (see Figures 12 and 13) that is enclosed in the 6 stylet shaft 124. The stylet carrier terminal extension portion 280 may be 7 formed as a spring to help maintain contact between the stylet carrier terminal 8 extension portion 280 and the stylet carrier contact 276. The stylet carrier 9 terminal 282 (with the extension portion 280) is fxed within the stylet foot 225, so that when the stylet foot 225 is removed from the stylet carrier 220, the 11 stylet carrier terminal 282 {with the extension portion 280) is removed with the 12 stylet foot 225. The extension portion 280 fits through an opening in the stylet 13 carrier 220 so that the extension portion may contact the stylet carrier contact 14 276.
A similar type of electrical path is provided for the cannula conductor 16 142 that is contained in the cannula 112. A c;annula carrier terminal 286 is 17 fixed within the cannula foot 229, which is removably mounted in the cannuia , 18 carrier 210, as previously described. The cannula carrier terminal 286 is in 19 electrical contact with the cannula conductor 144 that is enclosed within the cannula tube 140. (See also Figure 10.) The cannula carrier terminal 286 has 21 a spring extension portion 288 that is in contract with a cannula carrier contact 22 290 when the cannula foot 229 is mounted in the cannula earner 210. A
23 cannula wire 292 provides an electrical current path between the cannula 24 carrier contact 290 with the cannula base contact 270 that is embedded in the base end piece 232. Again, because the position of the cannula slide 210 26 changes with respect to the base end piece 232, the cannula wire 292 is 27 advantageously a coiled wire wrapped around a longitudinal pin 294.
28 A series of electrical contacts and electrical wires substantially similar _ WO 00/16697 PCTJUS99/21416 - 1 to those for providing the electrical current path for the cannula conductor 144 2 may be provided in the bipolar configuration in which a return electrode 152 is 3 included in the cannula 112. For example, tile return electrical path may be 4 included on the opposite side of the cannula carrier 220 for providing contact between the cannula return electrode 152 and the return base contact 272 that 6 is embedded in the base end piece 232. A return electrode 298 embedded in 7 the electrically insulating cannula foot 229 {:Figures 10 and 11 ) provides a 8 portion of such electrical contact. A coiled return wire 302 (Figures 4 and 5) 9 provides an electrical current path between fhe return electrode 298 -and the return base contact 272 embedded in the base end piece 232. The coiled return 11 wire 302 may be wrapped around a supporting longitudinal pin 304.
12 A method of performing a biopsy in aiccordance with an aspect of the 13 present invention will be described with reference to Figures I 8 through 21.
14 Refernng first to Figure I 8, a portion of human tissue, such as a human breast 4I0, is illustrated containing several tissue rr~asses 420, which may be 16 suspected tumors or lesions to be examined. Through an incision in the tissue 17 410; the portion of the biopsy probe 102 containing the stylet 1 L0 and the 18 distal end of the cannula 112 is inserted, using RF current, until the stylet head 19 122 is near a targeted tissue mass 420. The probe 102 is guided toward the targeted tissue mass 420 using conventional imaging techniques, such as 21 ultrasound or X-rays. The stylet 110 and the. cannula 1 I2 are both in their 22 withdrawn (proximal) positions, as illustrated in Figure 4. Insertion of the 23 probe 102 toward the targeted tissue mass 420 may be assisted by energizing 24 the stylet electrode I26 to ablate subcutaneous tissue between the skin and the targeted tissue mass 420. As shown in Figure 19, while the probe 102 is being 26 inserted to access the targeted tissue mass 42;0, the stylet I 10 is in its 27 withdrawn position relative to the distal end of the cannula 1 I2, so that stylet 28 head 122 abuts or substantially abuts the disl;al end of the cannula 112, closing 1 the opening in the distal end of the cannula 112, and thus the passage 148.
2 The stylet electrode 126 is then electrically activated to ablate the tissue 3 of the targeted tissue mass 420. The stylet head 122 is then pushed through 4 the tissue mass 420, creating an opening through the tissue mass 420 as the stylet 110 penetrates the tissue mass by moving distally toward its extended 6 position, while the cannula 112 remains in its proximal position; so that the 7 stylet head 122 separates from the distal end of the cannula 112. A gap is thus 8 opened between the stylet head 122 and the distal end of the cannula 112. A
9 portion of the tissue mass 420 f lls in this gap between the stylet head 122 and the cannula 112, around the stylet shaft 124. A particular advantage of the 11 arcuate stylet electrode 126 is that it creates ~a narrow "slice" through the 12 targeted tissue mass 420, thereby facilitating the filling of the aforesaid gap 13 with the portions of the tissue mass on either side of the "slice" that collapse 14 into the gap after being pushed outwardly by the passage of the stylet head 122.
16 The stylet electrode 126 may then be deactivated, and the cannula 17 electrode 142 activated. With the cannula electrode 142 activated, the portion 18 of the tissue mass 420 adjacent the cannula electrode 142 is ablated, and the 19 cannula 112 may be pushed forward through. the portion of the tissue mass that has filled in around the stylet shaft 124. As the cannula 112 moves 21 through the tissue mass 420, it cuts off a portion of the tissue mass 420, and 22 encases that portion in the annular channel 148 within the cannula 112.
Once 23 the cannula 112 has closed the gap between the distal end of the cannula 24 and the stylet head 122, the severed portion of the tissue mass 420 is contained within the annular channel 148 of the cannula 112. The entire probe 102 may 26 then be removed from the tissue mass 420 and the patient's body. Once 27 removed, the cannula 112 and the stylet 110 may again be separated, and the 28 tumor portion contained within the annular channel 148 of the cannula 112 WO 00/16697 PCTlUS99121416 - 1 removed for examination and analysis. .
2 Using the device and method of the present invention, the removal of 3 tissue specimens may proceed at a slower pace than is typically possible using 4 conventional spring-activated knife cutters. fn particular, additional time can S be allowed between the insertion of the stylet through the suspicious tissue, 6 and the insertion of the annular cannula. This additional time allows more of 7 the tissue to fill the space surrounding the st5~let shaft 124, allowing the 8 cannula electrode 142 to cut a larger sample of the suspicious tissue than has 9 typically been possible using the cutters of the prior art. In addition, the stylet and cannula of the present invention are less likely to be deflected as they 11 move through the tissue then are the mechanical cutters of prior art biopsy 12 devices.
i 3 The specific embodiments described and illustrated above are 14 exemplary, and not exhaustive or exclusive. Those familiar with the art will i 5 recognize that various modifications may be made to the specific embodiments 16 described above without departing from the concepts of the present invention.
17 For example, those skilled in the art will recognize that various modifications 18 may be made to the base unit, and that different configurations may be used 19 for controlling the movement and position of the stylet and the cannula. In addition, different specific shapes of the stylet, the stylet head, and cannula 21 may be incorporated into a system implernen;ting the present invention.
22 Furthermore, although an electric motor is th.e preferred mechanism for 23 driving the cannula carrier and the stylet cart~ier, other mechanisms, such as 24 mechanical springs or pneumatic mechanismrs, may be employed. Indeed, a simplified device may employ manually-driven earners. Moreover, although 26 RF energy is preferred to effect the tissue ablation, other types of energy (e.g., 27 microwave, ultrasound, or laser) may be employed instead, as mentioned 28 above. These and other modifications and variations that may suggest II

WO 00/t6697 PCT/US99/2t4t6 I themselves are considered to be within the spirit and scope of the present 2 invention, as defined in the claims that follow.

Claims

1. An electrosurgical stylet, comprising:
a shaft having a proximal end and a distal end;
a stylet head disposed on the distal end of the shaft; and a tissue ablation electrode formed of a length of electrical conductor which extends over a distal end surface of the stylet head spaced distally from the distal end surface.

2. The electrosurgical stylet of Claim 1, wherein the stylet head has a substantially hemispherical distal end surface.

3. A biopsy device, comprising:
an elongate cannula having an open distal end and a proximal end;
a tissue ablation element disposed on the open distal end of the cannula;
an elongate stylet slidably disposed within the cannula configured for axial translation between an extended position and a withdrawn position; and a tissue ablation electrode disposed on a distal end of the stylet.

4. The biopsy device of Claim 3, wherein the stylet comprises:
a shaft having a proximal end and a distal end; and a substantially hemispherical stylet head disposed on the distal end of the shaft, the tissue ablation electrode extending over a distal, end surface of the stylet head.

5. The biopsy device of Claim 4, wherein the tissue ablation element disposed on the open distal end of the cannula is also an electrode.

6. The biopsy device of Claim 3, wherein the stylet comprises:
a shaft having a proximal end and a distal end; and a conical head terminating in an apex portion, wherein the tissue ablation electrode includes the apex portion.

7. The biopsy device of Claim 3, further comprising a stylet translation mechanism coupled to the stylet for translating the stylet within the cannula between the withdrawn and extended positions.

8. The biopsy device of Claim 7, wherein the biopsy device includes a base, wherein the stylet has a proximal end extending proximally from the proximal end of the cannula, and wherein the translation mechanism comprises:
a carrier connected to the proximal end of the stylet and movably mounted on the base, the carrier being movable on the base between a first position in which the stylet is in the withdrawn position and a second position in which the stylet is in the extended position; and a carrier drive, coupled to the carrier, for moving the carrier between the first and second positions.

9. The biopsy device of Claim 8, wherein the carrier drive is driven by a motor.

10. The biopsy device of Claim 9, wherein the motor has a drive shaft, and wherein the carrier drive comprises:
a drive screw coupled for rotation with the drive shaft;
a screw-driven mechanism coupled between. the drive screw and the carrier, whereby rotation of the drive screw in a first direction moves the carrier from the first position to the second position.

11. A biopsy device, comprising:
a base having a proximal end and a distal end;
an elongate cannula having an open distal egad and an open proximal end mounted on the base for axial translation thereon between a proximal position and a distal position;
an elongate stylet slidably disposed within the cannula, the stylet having a proximal end that extends proximally from the proximal end of the cannula and that is mounted on the base for axial translation between a withdrawn position and an extended position with respect to the cannula;
a first tissue ablation element disposes on the open distal end of the cannula;
a second tissue ablation element disposed on a distal end of the stylet; and a translation mechanism for sequentially moving the stylet from its withdrawn position to its extended position, and then moving the cannula from its proximal position to its distal position.

12. The biopsy device of Claim 11, wherein the translation mechanism comprises:
a first carrier, connected to the proximal end of the stylet and slidably mounted on the base for translation thereon between a first position corresponding to the withdrawn position of the stylet and a second position corresponding to the extended position of the stylet;
a second carrier, connected to the proximal end of the cannula and slidably mounted on the base between the first corner and the distal end of the base, for translation thereon between a proximal position corresponding to the proximal position of the cannula and a distal position corresponding to the distal position of the cannula; and a carrier drive engageable with the first and second carriers, for sequentially driving the first carrier from its first position to its second position and then driving the second carrier from its proximal position to its distal position.

13. The biopsy device of Claim i2, wherein the carrier drive comprises:
a motor having a drive shaft;
a drive screw coupled for rotation with the drive shaft;
a screw driven mechanism coupled between the drive screw and the first carrier, whereby rotation of the drive screw in a first direction moves the first corner from the first position to the second position.

14. The biopsy device of Claim 11, wherein the first and second tissue ablation elements are activated by radio frequency electrical current.

15. The biopsy device of Claim 12, wherein the stylet is removably mounted in the first carrier and the cannula is removably mounted in the second carrier.

16. The biopsy device of Claim 11, wherein the stylet comprises:
a shaft having a proximal end and a distal end and defining a longitudinal axis therebetween; and a substantially hemispherical stylet head disposed on the distal end of the shaft with the second tissue ablation element extending distally from the head.

17. The biopsy device of Claim 16, wherein the first and second ablation elements are energized by radio frequency electrical current, and wherein the second ablation element comprises an arcuate length of electrical conductor having a radius of curvature that is substantially coplanar with the longitudinal axis of the shaft.

18. The biopsy device of Claim 14, wherein the first ablation element is an ablation electrode, and wherein the cannula includes a return electrode spaced from the ablation electrode.

19. The biopsy device of Claim 18, wherein the cannula includes an elongate aperture along a portion of its length, and wherein the retain electrode comprises a length of conductor, contained within We cannula, at least a portion of the conductor being exposed through the elongate aperture.

20. A method of taking a tissue sample from a targeted subcutaneous tissue mass within the body of a patient, comprising:
a) providing a probe comprising:
a cannula having an open distal end, a stylet disposed within the probe for axial movement therein between a withdrawn position and an extended position relative to the distal end of the cannula, a first tissue ablation element disposed on the open distal end of the cannula, and a second tissue ablation element disposed on a distal end of the stylet;
b) while activating the second ablation element with energy of a type and quantity that causes tissue ablation, advancing the probe by tissue ablation, with the stylet in the withdrawn position, into the patient's body toward the targeted tissue mass;
c) with the second ablation element activated, moving the stylet to its extended position so that it penetrates the targeted tissue mass by ablation, while creating a gap between the second ablation element and the distal end of the cannula that fills with a portion of the tissue from the targeted tissue mass;
d) while activating the first ablation element with energy of a type and quantity that causes tissue ablation, moving the cannula distally relative to the stylet so as to close the gap, thereby capturing the portion of the tissue mass within the cannula; and e) withdrawing the probe from the body with the portion of the tissue mass captured within the cannula.

21. The method of Claim 20, wherein the first arid second ablation elements are activated with radio frequency electrical current.

22. The method of Claim 20, wherein the stylet anal the cannula are movably mounted on a base, wherein the cannula is movable between a proximal position and a distal position relative to the base, wherein the cannula is in the proximal position during advancing the probe and of moving the stylet, and wherein moving the cannula includes moving the cannula from its proximal position to its distal position.

23. The method of Claim 20, wherein moving the stylet and moving the cannula are performed by an electrically powered driving mechanism.

24. The method of Claim 20, wherein moving the stylet creates a narrow slice through the targeted tissue mass.

25. The electrosurgical stylet of Claim 1, wherein the tissue ablation electrode comprises an arcuate length of electrical conductor having a radius of curvature that is substantially coplanar with a longitudinal axis of the shaft.

26. The electrosurgical stylet of Claim 1, wherein the tissue ablation electrode is formed from a length of electrical conductor which protrudes from diametrically opposed sides of the stylet head and extends over the distal end surface of the stylet head spaced distally from the distal end surface.

27. The biopsy device of Claim 5, wherein the second ablation element comprises an arcuate length of electrical conductor having a radius of curvature that is substantially coplanar with a longitudinal axis of the shaft.