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Message: <blockquote data-quote="amila_90210" data-source="post: 4088873" data-attributes="member: 111009">Biopsy The biopsy should usually be the final staging procedure.  Although the biopsy can distort the imaging studies, such as MRI, pathologic  evaluation and interpretation may require information provided by the prior  workup. Complications relating to the biopsy are not infrequent. Accordingly,  careful preoperative planning is imperative. The imaging studies aid the surgeon  in selecting the best site for a tissue diagnosis. In most cases, the best  diagnostic tissue is found at the periphery of the tumor, where it interfaces  with normal tissue. For example, in the case of a malignant bone tumor,  soft-tissue invasion is usually evident outside the bone, and this area can be  sampled without violating cortical bone and thus without causing a fracture at  the biopsy site. If a medullary specimen is needed, a small round or oval hole  should be cut to decrease the chance of fracture. If the medullary specimen is  malignant, the cortical hole should be plugged with bone wax or bone cement to  reduce soft-tissue contamination following the procedure. Obtaining an adequate specimen is critical. A frozen  section determines if viable and adequate tissue were obtained. A few  experienced tumor centers may make a definitive diagnosis based on a frozen  section, allowing the surgeon to proceed with definitive operative treatment of  the tumor. However, freezing artifact can cause overinterpretation of the  material, so an aggressive resection should always be deferred until the  permanent analysis is complete. Additional studies beyond conventional light  microscopy, such as immunocytochemistries and cytogenetics, may also be  necessary. The placement of the biopsy site is a major consideration.  If the surgeon is inexperienced and not familiar with surgical oncologic  principles, a serious contamination of a vital structure such as the popliteal  artery or sciatic nerve may occur. Such an error might necessitate an amputation  instead of a limb-sparing procedure. To avoid this problem in the case of a  suspected malignant condition, the surgeon who performs the biopsy should be the  same surgeon who will perform the definitive operative procedure. Transverse incisions should be avoided because removing the  entire biopsy site with the widely resected subjacent tumor mass is difficult.  Adequate hemostasis is mandatory to avoid formation of a contaminating hematoma.  A drain may be helpful but frequently is unnecessary. If a drain is used, it  must be placed in line with the incision. Needle biopsies, either core or fine needle, can be used by  experienced tumor centers, especially for lesions that are easily diagnosed,  such as metastatic carcinomas or round cell tumors. Because the subtype of  sarcoma is proving to be very important, architecture of the tumor is generally  needed, which requires a core biopsy rather than a fine-needle aspirate. Core  biopsies also allow the surgeon to sample various areas of the tumor to avoid  sampling error in a heterogeneous tumor. In the case of a deep pelvic lesion or  a spinal lesion, a CT-guided needle biopsy is ideal because it avoids excessive  multicompartmental contamination. In general, excisional biopsies are discouraged unless the  lesion is particularly small (less than 2–3 cm) or in an area where a cuff of  healthy uninvolved tissue of at least 1 cm can be removed as well. This  technique ideally avoids a second procedure to remove the entire biopsy site if  the lesion turns out to be malignant. Cultures and Special Studies The damage of biopsy specimens after retrieval can make it  impossible to perform special studies such as immunohistochemistry,  cytogenetics, flow cytometry, and electron microscopy. For this reason, the  biopsy surgeon should consult with the pathologist before specimens are  retrieved and handled. Furthermore, many current studies require fresh tissue  (no formalin). It is also a good habit to obtain cultures for bacterial culture  (anaerobic and aerobic) as well as fungal and acid-fast bacteria if clinical  suspicion warrants. Molecular diagnostics is on the verge of revolutionizing  sarcoma diagnostics. Specific translocations were found in a variety of tumors  (Table 6–7). Furthermore, therapeutics are beginning to be designed against  specific molecular defects in malignancies. Gastrointestinal stromal tumor  (GIST), a malignant mesenchymal tumor arising from the gastrointestinal (GI)  tract, omentum, and mesentery, overexpresses a mutant form of c-kit. The  KIT gene encodes a tyrosine kinase receptor for the growth factor named  stem cell factor or mast cell growth factor. Therapy directed against  c-kit is having an early and remarkable effect on the previously  difficult treatment of malignancy. Similar pathways are being elicited in other  sarcomas</blockquote>

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