A 41-year-old man attended our clinic with massive gastrointestinal bleeding due to a tumor of the small intestine. The tumor was not diagnosed until during acute laparotomy. The histological examination revealed a gastrointestinal stromal tumor with uncertain biological behaviour. The authors discuss the rare gastrointestinal stromal tumors, where preoperative diagnosis is difficult and in symptomatic forms urgent laparotomy is usually the only diagnostic method. The differential diagnosis between leiomyoma, schwannoma, mesenterial fibromatosis or intraabdominal solitary fibrous tumor as well as metastatic melanoma is not simple and immunohistochemistry plays a leading role. Prediction of biological behaviour of these tumors is also problematic and depends on the histological picture, site, size and mitotic activity.

        Key words: stromal tumors - symptomatology - diagnosis - immunohistochemistry