"Getting a Biopsy!" TUMOR TIDBITS, A BIWEEKLY VETERINARY ONCOLOGY E-LETTER Volume 2; Number 15; September 15, 2001. Editor: Kevin A. Hahn, DVM, PhD, Dipl - ACVIM (Oncology) & Overall Nice Guy! ONGOING ANNOUNCEMENTS FROM ONCOLOGY (www.gcvs.com) 1 - Dr. Hahn is available for appointments in our Tomball Office on every other Monday (713-693-1166) and in our San Antonio Office (210-822-1913) on every Thursday in addition to our regular office hours in Houston. 2 - Dr. Hahn has 2 really great residents, Drs. Freeman & Turner, available in Houston Monday through Friday (hey - if you got it, flaunt it right? They work with Drs. Hahn & King along with our 2 Board Certified Radiologists and 3 Radiology Residents - what a TEAM!). 3 - Don't forget Clinical Trials. Our plasmid therapy is helping many pets with chronic illnesses. We are accepting new patients for this trial every Tuesday and Wednesday. Plans are upcoming for a nationwide start. 4 - The Annual Veterinary Cancer Society Meeting is October 11-13 in Baton Rouge - Don't miss it! Email Dr. Hahn for further information. THIS WEEK'S TUMOR TIDBIT: GETTING A BIOPSY! WHEN SHOULD YOU OBTAIN A BIOPSY? A preoperative biopsy should be obtained if it will change your choice of therapeutic modality or if it will alter the degree or extent of therapy you choose. For example, it is very important to know the tumor type prior to surgery of the appendicular skeleton. Soft tissue sarcomas are locally invasive and aggressive tumors that usually require radical margin resection, whereas lipomas are benign and require only marginal resection (see lecture notes for a full discussion of margins). Pretreatment biopsies are also important if the knowledge that a pet has cancer will change the owner's willingness to treat his/her pet. Some owners are more willing to have their pet undergo a radical surgery, such as an amputation, if they know that there would be a good chance for cure, such as in the case of a fibrosarcoma. Some masses, due to their location within a body cavity, are difficult to biopsy preoperatively. For example, obtaining a representative sample of a splenic or a solitary lung mass usually requires an exploratory laparotomy or thoracotomy, respectively. In these particular examples, the surgical removal of the mass is both diagnostic and therapeutic. The surgical treatment in both these examples would not have changed, even if the tumor type had been known prior to surgery. Delaying obtaining a biopsy specimen until excision is also a possibility if retreatment is an option. For example, if a small skin mass on the trunk is excised with dirty margins, there is plenty of tissue left to reoperative without jeopardizing a cure with surgery. However, this would not necessarily be the same case with the same mass on the appendicular skeleton, where tissue for skin closure is at a premium. Tumors are not homogeneous tissue masses. They contain areas of inflammation, necrosis, and reactive tissue. In general, the larger the tissue samples-the better the diagnostic yield. Care should also be taken not to create excessive crush artifact with the surgical instrumentation when handling the biopsy sample. Cautery should be avoided on the biopsy specimen, as it alters the tissue architecture and cellular morphology. Adherence to aseptic technique reduces the chances of wound infection; however, all biopsy sites should be monitored closely for signs of infection and inflammation. Delayed healing at a tumor site may indicate wound infection and/or tumor regrowth. Cancer and coagulation abnormalities often go hand in hand. Thrombocytopenia, disseminated intravascular coagulation, and increased heparin production are the most common coagulation abnormalities seen with cancer. A coagulation panel and buccal mucosal bleeding time should be evaluated in all suspect cancer patients prior to an invasive biopsy procedure. Good preoperative biopsy technique will allow for excision and radiation of all biopsy tracts during definitive therapy. Gentle manipulation of the mass and the use of small gauge needles for aspiration will minimize tumor seeding. Even though there is a short-lived increase in cancer cells documented within the efferent vessels and lymphatics on tumor manipulation, there is no real risk of distant tumor metastasis. When performing a surgical biopsy, blunt dissection of the surrounding soft tissues should be minimized, and accurate hemostasis should be employed to prevent unnecessary local tumor seeding within the wound. In addition, biopsy sites should never be drained. BIOPSY NEEDLES CUTTING NEEDLES Various biopsy needles can be used for percutaneous biopsy. In general, newer automated needles are preferred. These are spring-loaded needles that are similar in style to manual Tru-Cut needles. Automated needles can be completely automatic or semi-automatic. Completely automatic needles thrust the inner obturator (containing the biopsy tray or specimen notch) followed by the outer cutting sheath into the organ in a fraction of a second. These needles can easily be operated with one hand. Since the action is so quick, there is minimal displacement of the organ, a shorter intra-parenchymal phase, and much more reliable yield of tissue. This allows the organ to be biopsied with minimal manual mobilization, allows a smaller diameter needle to be used, and a lighter degree of sedation. In addition, extremely soft tissues (such as lung) tend to be less fragmented by the rapid cutting action. SEMI-AUTOMATIC NEEDLES Semi-automatic needles require manual thrusting of the internal obturator (containing the biopsy tray or specimen notch) into the organ, followed by an automatic thrusting of the outer cutting sheath by the spring-loaded mechanism. These needles have some of the advantages of the completely automatic needles, and have the additional advantages of having more control over final needle position, being lighter with a smaller handle, and the tip of the needle can be precisely localized before the outer cutting sheath is "fired". The older manual cutting needles offer no advantages over these newer needles. ASPIRATION NEEDLES Aspiration needles are generally used to obtain smaller samples that would be suitable for cytologic preparations (rather than histopathology). These needles are also well suited to obtain samples of fluid, such as intraparenchymal cysts, loculated effusions, gall bladder puncture, etc. Usually these are smaller gauge needles (20 to 22 gauge) and therefore tend to be less traumatic. BIOPSY METHODS PUNCH BIOPSY Biopsy punches are disposable and available in diameters ranging from 2 mm to 6 mm. Generally, the larger biopsies are preferred so the pathologist has adequate tissue to make a histologic diagnosis. When possible, the junction between normal and abnormal tissue should be biopsied. Punch biopsies are usually inadequate to obtain tissue below the dermis; subcutaneous fat is rarely obtained in the average punch biopsy of the skin. The hair is clipped and the surgery site prepared with a surgical scrub. Using a 25-gauge needle, approximately 2 to 3 mls of the local anesthetic agent lidocaine are injected around the lesion. It is important to not distort or disturb with lidocaine, the normal architecture of the tissue to be biopsied. The biopsy area is scrubbed a final time after the lidocaine is injected. The skin is stretched between the thumb and index finger. The biopsy punch is placed at right angles to the skin surface. The punch is rotated in one direction while at the same time firm downward pressure is applied until the subcutis is reached. The punch is then angled almost parallel with the skin while still applying pressure along the long axis of the biopsy punch. The punch is rotated to sever the base of the biopsied material. The punch is removed. The core of tissue is gently elevated with the point of a needle and the base severed with scalpel or iris scissors. One to two sutures are placed to close the defect. INCISIONAL BIOPSY In some cases, the incisional biopsy is preferred over a punch biopsy because larger sections of tissue can be obtained for histologic diagnosis. In addition, if the lesion is biopsied at the junction of the normal and abnormal tissue, a "wedge" of tissue is obtained that retains a larger section of the tissue's architecture. This allows the histopathologist to better see characteristics of malignancy, such as invasion of normal tissue. The animal is placed under general anesthesia after routine screening tests have been performed to identify problems such as coagulopathies and metabolic disease. The hair is clipped and the surgery site prepared with a surgical scrub. After the region is draped, an elliptical or wedge incision is made at the margin of the normal and abnormal tissue. Care is taken to obtain adequate tissue and to ensure that a subsequent definitive surgery can successfully remove the tumor and the incisional biopsy incision. Vessels going to and from the tissue to be biopsied are carefully identified and ligated. The specimen is lifted and severed at the base with either scissors or a scalpel blade. The incision is sutured for closure. EXCISIONAL BIOPSY An excisional biopsy should be performed when tissue is required for a histologic diagnosis, but the lesion must be small enough and in an anatomic location that allows for wide surgical removal without compromising the normal tissue around it. In general, an excisional biopsy is preceded with at least fine needle aspirate cytology to give the surgeon as much information as possible about the characteristics of the tumor prior to removal. For example, a mast cell tumor or a soft tissue sarcoma would require wide surgical margins (2 to 3 cm), whereas a sebaceous cyst or sebaceous adenoma could be treated with smaller margins. This biopsy is performed in the same manner as an incisional biopsy except the lesion is excised completely, with adequate margins. NEEDLE CORE BIOPSY Needle core biopsy is generally safe and quick,and can be performed on an awake cooperative patient. The histopathologic results are generally more accurate than fine needle aspirate cytology, but not as accurate as excisional biopsy. The lymph node is grasped by an assistant and held firmly against the overlying skin, and the biopsy site is prepared as noted above. Approximately 2 to 3 mls of 2% lidocaine are injected under the skin overlying the enlarged lymph node. Using a number 11 surgical blade, a stab incision is made in the skin to allow ease of entry of the needle core biopsy instrument. The needle core biopsy instrument is advanced through the incision and into the capsule of the enlarged lymph node for subsequent biopsy. At least 3 to 5 biopsies are taken of the lymph node through the same stab incision. The needle biopsy specimens are fixed in 10% buffered formalin as described above. A separate container should be used for each lesion that is biopsied. The stab incision is sutured only if indicated. LYMPH NODE BIOPSY Lymph node biopsy is often important in the diagnosis, staging and proper therapeutic management of the pet with cancer. A biopsy is often performed after fine-needle aspirate cytology suggests the presence of a disease. Despite the accuracy of fine-needle aspirate cytology in determining certain diseases such as lymphoma, mast cell tumors, and the presence of metastatic solid tumors, a histopathologic diagnosis is always recommended prior to initiation of therapy. In each case, adequate tissue must be obtained for histopathologic diagnosis and special stains, if indicated. When possible, the submandibular lymph nodes should be avoided; they often are reactive in the normal animal because they drain the oral cavity where the bacterial count is usually quite high. These reactive cells are sometimes misdiagnosed as neoplastic cells. If a carcinoma or a sarcoma is suspected, a biopsy should not be performed unless an overall plan for definitive therapy is made because the biopsy procedure can "seed" the operative field with tumor cells if the principle of en bloc dissection is violated. As with all biopsies, the surgeon who will perform the definitive surgery should be consulted prior to the biopsy to ensure that incisions are properly placed for a subsequent definitive procedure. BIOPSY SPECIMEN HANDLING CONSIDERATIONS Pinch biopsy specimens should be removed from the forceps with the utmost of care. These minute specimens are readily subject to crush and squeeze artifact, particularly before fixation. Specimens should be teased from the forceps with a needle and gently placed upon lens paper or specially designed biopsy sponges presoaked in formalin. Attempts to reorient specimens on the surfaces should be avoided. After all specimens are placed on a suitable surface, the biopsies are immersed in formalin and submitted to the laboratory. Fixation in 10% neutral buffered formalin is adequate for routine histologic examination. Glutaraldehyde fixation is optimal for specimens for electron microscopic examination. Fresh frozen tissue (e.g., via liquid nitrogen) may be required for immunohistochemical studies of certain antigens. ANY OTHER QUESTIONS ABOUT BIOPSIES? Don't hesitate to call or email us at Gulf Coast Veterinary Oncology! We can forward additional info by email if needed. IN 2 WEEKS: What's the best treatment for Bladder Cancer???? ALL THE BEST, Kevin Hahn Kevin A. Hahn, DVM, PhD Diplomate ACVIM (Oncology) & Overall Nice Guy Gulf Coast Veterinary Specialists 1111 West Loop South, Suite 150 Houston, TX 77027 P: 713.693.1166 F: 713.693.1167 www.gcvs.com drhahn@gulfcoastvetspec.com