An Osteoclast-Rich Tumor of the Gastrointestinal Tract with Features Resembling Clear Cell Sarcoma of Soft Parts: Reports of 6 Casesof aGIST Simulator

Six cases are reported of an osteoclast-rich tumor of the gastrointestinal tract that should be segregated from GIST. Five of the cases were located in the small bowel and one in the stomach. The age of the patients ranged from 13 to 37 years. The tumors behaved aggressively, with metastases to regional lymph nodes, liver, and other intraabdominal sites. Microscopically, the tumor cells were medium-sized, predominantly oval, relatively monomorphic, diffusely immunoreactive for S-100-protein, and negative for CD1 17, CD34, HMB-45, and Mart-i. They were admixed with scattered osteoclast-like, multinucleated giant cells which were S-100-protein negative and KPIpositive. One case studied cytogenetically had the karyotype 46XX t(I2;22)(qI3;q12). The cases here reported are interpreted as examples ofa distinctive type of gastrointestinal neoplasm which shares somefeatures with clear cell sarcoma of soft parts (melanoma of soft parts), including in one case the chromosomal translocation that is characteristically associated with that entity.