To evaluate histologic subtype and grade, which in turn guide the decision making for multimodality therapy, the workup of suspected sarcoma requires more material than can be obtained from a fine-needle aspiration. Either open or percutaneous core needle biopsy is indicated before a management decision is made. Percutaneous biopsy of a potentially malignant lesion is controversial, given the perceived potential for tumor seeding along the needle tract. However, the evidence that the latter is a significant risk is weak at best. To the authors' knowledge, among cases of patients with extremity sarcoma who have undergone core needle biopsy, only a few cases of needle tract seeding have been reported to date. Although en bloc excision of the needle tract with the primary tumor is often performed, this practice is not associated with improved oncologic outcomes; the evidence for excision of the needle tract is poor. For patients with gastrointestinal stromal tumors, there is a theoretical risk of peritoneal dissemination after percutaneous biopsy, but to the authors' knowledge this remains unproven. Although endoscopic ultrasound is the preferred route for biopsy among patients with gastrointestinal stromal tumors, percutaneous biopsy is indicated if endoscopic ultrasound is unsuitable or unavailable. In the setting of retroperitoneal sarcoma, a review of pooled data from 4 large tertiary care referral centers demonstrated a risk of needle tract seeding of 0.37%. The authors concluded that the benefits of pretreatment biopsy in patients with mesenchymal tumors outweigh the potential risks of needle tract seeding. Cancer 2017;123:560-567. © 2016 American Cancer Society.

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