A Case of Gastrointestinal Stromal Tumor of the Rectum Immunohistochemically Positive for C-kit

Hiroshi Nozawa, Makoto Hirano, Nozomu Murakami, Yusuke Uno, Tsutomu Kikuchi, Toshiyuki Okuda, Junko Oya, Hirokatsu Kikkawa and Shinji Masuda^*

Department of Surgery, and Department of Pathology^*, Koseiren Takaoka Hospital

A 80-year-old man was admitted to our hospital because of melena and anal pain. Digital examination, colonoscopy, CT and MRI revealed a large sub-circular tumor in the lower rectum. Biopsy specimens revealed that the tumor was rectal GIST (gastrointestinal stromal tumor), because tumor cells were strongly positive for CD34, and we performed Miles' operation. The tumor looked SMT appearance with central ulceration, and mesured 11×7cm in diameter. The tumor had a capsule with no invasion beyond the capsule and no metastasis to the lymph nodes. Histologically, the tumor was composed of spindle shaped cells with few nuclear atypia and a few mitosis (4/10HPF) were observed. Tumor cell were strongly positive for CD34 and c-kit by immunohistochemical examination. This immunohistochemical diagnosis with c-kit has been necessary, because it has been considered GIST as being originated from interstitial cell of Cajal. We diagnosed this tumor as GIST in restricted sense, with no differentiation toward neural or musculer type interstitial tumor.

Key words
gastrointestinal stromal tumor, c-kit, CD34

Reprint requests
Hiroshi Nozawa Department of Surgery, Koseiren Takaoka Hospital 5-10 eiraku-cho, Takaoka, 933-8555 JAPAN

Accepted
November 29, 2000

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