A CASE OF GIANT GASTRIC STROMAL TUMOR (UNCOMMITTED TYPE) WITH METACHRONOUS METASTASIS TO THE LIVER, SPLEEN AND THE PERITONEUM

A 66-year-old woman was admitted to the hospital because of abdominal distention. Abdominal CT scan revealed a giant tumor extending from the left hypochondrium to lower abdomen. We suspected a leiomyosarcoma and performed an operation. The resected specimen was 30×2×17cm in size and 3274g in weight. The tumor existed in the submucosal layer to the subserosa of the upper body of the stomach with hematoma and necrosis in it. Histopathologically, atypical spindle cells proliferated and the cellularity was high. Approximately one mitosis was observed with each high-power field. Immunohistochemical study showed that the tumor was positive for vimentin, CD34 and c-kit but was negative for muscle or neural markers. Therefore, we diagnosed the tumor as a malignant uncommitted type gastrointestinal stromal tumor (GIST) of the stomach. Hepatic and splenic metastases and peritoneal dissemination occurred seven months after the operation. The biological mechanisms of uncommitted type GISTs have not been elucidated as yet. Further accumulation of cases of uncommitted type GIST is expected to clarify the malignant potential or the mechanism of metastasis of uncommitted type GISTs. We report a case of giant uncommitted type GIST of the stomach supposed having high grade of malignancy which relapsed in a short time after the operation.