title: A case of a gastrointestinal stromal tumor with skeinoid fibers of the sigmoid colon.
abstract: An 80-year-old man was diagnosed with rectal cancer and underwent Hartmann's procedure. Although no tumors were identified during the preoperative examination, gross examination of the resected specimen incidentally revealed a submucosal tumor that was 9 mm in diameter at the oral side and located in the proximal stump of the specimen from the sigmoid colon. We suspected a concurrent gastrointestinal stromal tumor (GIST) and performed a histopathological examination. An L-shaped nodular lesion measuring 9 × 6 mm was histologically composed of a patternless proliferation of spindle cells intermingled with eosinophilic globules. Cellular atypia, prominent mitotic figures and necrotic foci were not observed in the nodule. The spindle cells were positive for CD34, CD117 and vimentin, but negative for CD56, smooth muscle actin and S-100 protein. MIB-1 positivity was estimated to be as low as approximately 1-2%. Electron microscopy showed a bundle of wool-like fibers with a periodicity of approximately 40 nm. We therefore considered the lesion to be a low-risk GIST with skeinoid fibers in the large intestine. Although numerous previous reports have reported skeinoid fibers in the stomach and small intestines, there have been only 9 cases (including the present case) of skeinoid fibers in the large intestine.
authors.affiliation: Department of Gastroenterological Surgery and Transplant Surgery, Tokyo Medical University, Tokyo, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Sumi
authors.affiliation: Third Department of Surgery, Tokyo Medical University, Tokyo, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Katsumata
authors.affiliation: Central Clinical Laboratory, Tokyo Medical University, Tokyo, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shibuya
authors.affiliation: Department of Gastroenterological Surgery and Transplant Surgery, Tokyo Medical University, Tokyo, Japan.
authors.forename: Sou
authors.initials: S
authors.lastname: Katayanagi
authors.affiliation: Department of Gastroenterological Surgery and Transplant Surgery, Tokyo Medical University, Tokyo, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Iwasaki
authors.affiliation: Third Department of Surgery, Tokyo Medical University, Tokyo, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kasuya
authors.affiliation: Department of Pathology, Tokyo Medical University Hachioji Medical Center, Tokyo Medical University, Tokyo, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Serizawa
authors.affiliation: Department of Gastroenterological Surgery and Transplant Surgery, Tokyo Medical University, Tokyo, Japan.
authors.forename: Motohide
authors.initials: M
authors.lastname: Shimazu
authors.affiliation: Third Department of Surgery, Tokyo Medical University, Tokyo, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Tsuchida
keywords: Gastrointestinal stromal tumors; Sigmoid colon; Skeinoid fiber