GIST part 3

Retroperitoneal Sarcoma or GIST?

Retroperitoneal and visceral sarcomas account for approximately 30% of all sarcomas. The most common histopathologic types in the retroperitoneum are liposarcoma, leiomyosarcoma, malignant peripheral nerve sheath tumor (MPNST), and fibrosarcoma. In the visceral location GIST, leiomyosarcoma, and desmoid are the most common histologic types seen. Malignant GIST is a type of sarcoma, comprising tumors of mesenchymal origin. Its diagnosis is based on documentation of c-KIT and PDGFα receptors. Before the diagnosis of GIST was possible, all cases had been classified as sarcomas. The aim of this retrospective analysis is pathological revision of all cases formerly diagnosed as gastrointestinal related mesenchymal tumors, in order to find hidden cases of GIST. Based on our study, any malignant mesenchymal mass located along or near the proximal GIT, and found to be c-kit negative, should be stained also for PDGFRα, in order to differentiate between GIST and other STS.