[A case of leiomyosarcoma of the duodenum--histologic diagnostic criteria of borderline malignancy].

A case of a leiomyosarcoma of the duodenum is reported. A 52-year-old man with a duodenal submucosal tumor underwent a pancreatico-duodenectomy. Histologically, the resected tumor revealed moderate cellular atypism and moderate pleomorphism, but revealed no mitotic figures. The histological diagnosis was leiomyoma. Nine years after operation, the tumor showed a recurrence and metastasis in the liver. Thus, the patient underwent a lobectomy of the liver. The resected liver tumor showed similar histological features seen in the primary duodenal tumor but with high mitotic activity. Histologically, the patient was diagnosed as having a metastatic leiomyosarcoma. This history suggests that a smooth muscle tumor of potential malignancy, as seen in this case, should be followed continuously, even though mitoses may not be recognized.