GIST: Biopsy Preoperative biopsy of a resectable mass is commonly performed but is associated with risks Biopsy is necessary if: Suspecting another cancer such as lymphoma or other sarcoma Considering neoadjuvant therapy or therapy for metastatic disease Casali et al. Ann On col 2008; 19(suppl 2): 1135-1i38 Demetri et al. J Natl Compr Can c Netw. 2007: 5(suppl 2) S1-29