biopsy in musculoskeletal tumors

diagnosis of bone tumors is based on careful evaluation of clinical, imaging and a pathologic findings. so the biopsy of bone and soft tissue sarcomas is the final step in evaluation and a fundamental step in the diagnosis of the lesion. it should not be performed as a shortcut to diagnosis (1). the biopsy should be performed in order to confirm the diagnosis and differentiate among few diagnoses after careful staged studies. real and artificial changes in imaging studies will be superimposed after performing biopsy, which may alter the interpretation if done after biopsy is taken (1). the correct management of a sarcoma depends on the accurate diagnosis. inadequate, inapprppriate, or inaccurate non-representative biopsy leads to poorer outcome in terms of survivorship and limb salvage. an incorrect, unplanned incision and biopsy may unnecessarily contaminate uninvolved compartments which may convert a salvageable limb to amputation. anatomic approach along with the proper biopsy techniques may lead to success or catastrophe. it is clear that in patients with inappropriate biopsy, the chance of the need to change the treatment to more radical than would originally be expected is significantly higher. also it is more probable to need to  convert curative to palliative treatment and to require adjuvant radiotherapy in patients with inappropriate biopsies. patients with sarcoma are best served by early referral to a specialized center where staged investigations and biopsy can be performed with minimal morbidity (3). open biopsy is still considered the gold standard; however, recent studies suggest comparable results with percutaneous core needle biopsy. our study on 103 consecutive cnb and open biopsy showed comparable results as well. surgeons need to answer to two questions prior to performing a biopsy: 1-          where is the best part of the lesion to be biopsied? 2-          what is the safest route without contaminating other anatomic structures? (4) carcinomas are homogeneous, and a simple cnb is usually sufficient for diagnosis, but in soft tissue sarcomas, the periphery of the tumor is the growing part and usually represents the authentic underlying malignancy. the center of the tumor may be hemorrhagic or necrotic, thus taking biopsy from this part may distract from the correct diagnosis.extraosseus part of a bone sarcoma is as representative as bony component of the tumor. violating the bone and weakening the cortex may predispose it to pathologic fracture, so biopsy of an extraosseus part is sufficient for the diagnosis if present (3). the biopsy tract “open or cnb” is contaminated by tumor cells and should be widely excised if a wide excision or amputation is performed. for this reason, excision of the biopsy incision or needle entrance should be planned along with the definitive tumor excision to prevent complications and the need for altering the treatment strategy (figure a, b, c). open incisional biopsy provides sufficient material for microscopic diagnosis as well as immune- histochemical, cytogenetic, or electron microscopic studies. it has some disadvantages such as wound healing problems, infection, tumor cell contamination, and nerve and vessel injuries (1). for open biopsies, the incision should be as small as necessary and longitudinal. transverse incisions are not advisable. to perform an intraosseus biopsy, the window should be circular or oblong, and as small as needed to prevent a pathologic fracture. closing this window by pmma prevents tumor cell contamination. compressing the pmma exceeds the chance of metastasis. as a rule, culture what you biopsy and biopsy what you culture. use of a tourniquet without exsanguinations helps better visualization and meticulous hemostasis which prevents spreading of the tumor cells in hematoma. importantly, it should be deflated before closing the wound (3). the port of entry of drains, if necessary, must be in line and proximity to the skin incision, because this tract is also contaminated and must be excised with the surgical specimen. imaging-guided core needle biopsy is a well-established technique for the diagnosis of bone and soft tissue tumors and tumor-like lesions in specialized orthopedic oncology centers. although large lesions of the limbs can easily be biopsied without image guidance, lesions in the spine, para spinal area, and pelvis are difficult to target, therefore taking the advantage of c.t. guidance will improve the accuracy of targeting the lesion for biopsy purposes. we can benefit from image intensifiers for targeting limb lesions rather than c.t. guidance. also sonographic guide can be applied for soft tissue lesions (figure d, e, f). in soft tissue tumors, the results of percutaneous cnb are relatively inferior compared to open biopsy whereas almost equal results are expected for bony tumors except for low-grade chondrosarcoma. cnb is a safe, minimally invasive, and cost effective technique for the diagnosis of bone lesions if done by an experienced orthopedic oncologic surgeon and be evaluated by an experienced anatomical bone pathologist (1, 3). for soft tissue tumors, cnb results depend on the size of the lesion, its location and amount of tumor necrosis. guided needle biopsy have become the standard technique in most orthopedic oncologic centers. the accuracy of this method in our center is more than 90% for bone tumors. cores should be taken in different directions including areas of central necrotic tissues but from a single well planned entrance. the procedure is quick, especially for bone cnb or soft tissue fna and cnb, and the diagnosis can be achieved within 24 – 48 hours. the material should be sufficient for immunohistochemistry evaluations as well (1-3). because i have seen 3 cases of tumor implantation at the towel clips puncture site including 2 chondrosarcomas and a case of malignant schowanoma, so i highly suggest that never crush the skin by towel clips especially when you do an open incisional biopsy (4). in summery open, needle or core biopsies should be performed by a surgeon who is responsible for definitive surgery of a tumor after complete staged evaluation to minimize the biopsy complications if we expect a successful outcome and longer survival (1-3).