Patient. 46 years old. Female. Has been ill since 6 month. Has not another diseases. Family history free. Endoscopy has shown submucosal lesion with infiltrative tumor on the antrum. The size of the submocosal lesion was 2,5 x 3.0 cm. The overlying mucosa in the middle of the submucosal lesion was ulterated. The biopsies have taken from both sites. Histologic examination of infiltrative region revealed adenocarcinoma G3. Biopsies of submucosal lesion was negative. The physical examination and routine laboratory tests upon admission were unremarkable. The histopathologic examination after operation has revealed an adenocarcinoma G3 of stomach, that has been infiltrating into the muscular layer. In microscopic examination of submucosal lesion have been found a spindle cells neoplasm located in muscularis propria extending up to serosa. In immunohistochemical studing for desmin and CD-117 which confermed the diagnosis of gastrointestinal stromal tumor. The mitotic count was 6/50 HPF. Also, in the side with ulceration of GIST have been found cells of adenocarcinoma. The patient has been undergone distal subtotal gastrectomy and Billroth-II gastrojejunal anastomosis with D2 lymphadenectomy. The patient has not received imatinibas adjuvant therapy for the GIST, according to the international guidelines for GISTs risk stratification. The patient underwent regular clinical and radiological follow-up every 4 months after discharge. No evidence of tumor recurrence was found after 12 months of follow-up.