Gastrointestinal stromal tumor with skeinoid fibers of the ileum

Gastrointestinal stromal tumor (GIST) is not uncommon among gastrointestina l nonepithelial tumors, but there are few reports describing the cytologic findings. We report a case of GIST with skeinoid fibers in scrape cytology preparation. The patient was a 53-year-old man with a tumor in the small in testine. Scrape preparations from the cut surface of the resected tumor rev ealed cellular material composed of spindle cells, elongated or cigar-shape d, and relatively uniform. The cytoplasm was fragile and demonstrated a fin ely fibrillar material. Dense hyaline materials with irregular outline were observed within the loose clusters composed of the tumor cells. The hyalin e materials were also observed in the background. Histologic preparation sh owed spindle cells arranged in a fascicular or storiform pattern. Most eosi nophilic globules were distributed between the tumor cells. The globules we re positive in periodic acid-Schiff reaction, and were stained blue with Ma sson's trichrome stain. Immunohistochemically, the tumor cells were strongl y and diffusely positive for c-kit, focally and weakly positive for alpha-s mooth muscle actin, and negative CD34 and S-100 protein. We emphasize that skeinoid fibers are characteristic of GIST arising in the small intestine, and there presence predicts a good prognosis, even in malignant GIST. (C) 2 000 Wiley-Liss, Inc.