1999 Volume 52 Issue 5 Pages 424-430
A case of GIST (gastrointestinal stromal tumor), arising in the rectum was reported, “GIST” has been applied to mesenchymal tumors that represent neither typical features of leiomyomas, leiomyosarcomas nor Schwannomas. Ultrasonography, colonoscopy, CT and MRI revealed a submucosal tumor in the lower rectum and aspiration cytology revealed that the tumor may have derived from smooth muscle, leiomyosarcoma. The tumor measured approximately 7 cm in diameter and was removed surgically. But immunohistochemical study showed that the tumor cells were negative for SMA and desmin, and focally positive for S-100 protein and NSE, and strongly positive for CD-34 and c-kit. An ultrastructural study failed to show any differentiation toward either cell type, which made the final diagnosis of rectal stromal tumor with focal neural differentiation.
In literatur, 71 rectal tumors of 941 gastrointestinal myogenic and neurogenic tumors between 1986 and 1996 were reported in Japan. Of these 71, immuohistochemical study was done only in 9 cases, out of which diagnosis of 7 cases were controversial in comparison with the definition of the GIST. Thus it was thought that many cases with GIST were included in the 941 reported cases.
Immunohistochemical and ultrastructural studies are necessary for the differential diagnosis of GIST, and gastrointestinal surgeons and pathologists must recognize GIST.
