An entity that should be kept in mind: Synchronous gastrointestinal stromal tumor encountered in resection materials obtained for the detection of intra-abdominal malignancies.

Objective: Gastrointestinal stromal tumors (GISTs), often sporadic, arise from interstitial Cajal cells of the gastrointestinal tract or their stem cell-like precursors. Apart from tumor-associated syndromes, it has been reported that GISTs are also associated with other tumors. There is no clear information about the etiology of these synchronous tumors. In this study, we wanted to present the clinicopathological features of 13 cases diagnosed as synchronous GIST with other tumors.

Methods: Demographic characteristics of the cases, risk of progressive disease score, tumor localization, size, and the mitotic activity of tumors along with survival status were evaluated.

Results: Thirteen of 101 cases diagnosed with GIST had a primary tumor synchronous with GIST. Synchronous GISTs were located in the stomach and small intestine. Most of the cases were detected incidentally in the intraoperative and post-operative periods. Risk scores for progressive disease were categorized as low (n=1), very low (n=1), and no risk (n=11). Non-GIST tumors were located in the stomach, transverse colon, left colon, rectum, gallbladder, kidney, and retroperitoneal space. Histological tumor types were adenocarcinoma, diffuse large B-cell lymphoma, mesothelioma, and neuroendocrine tumor. Life expectancy was found to be significantly lower in synchronous GISTs.

Conclusion: In cases operated for non-GIST tumors, the possibility of incidental detection of GIST should always be kept in mind.