Synchronous and metachronous neoplasms of different histogenesis with gastrointestinal stromal tumor (GIST): 10 years experience of a single institution.

AIM:Gastrointestinal stromal tumors (GISTs) are the most common primary mesenchymal neoplasms of the gastrointestinal tract. Significant advances have been made in its pathogenesis, diagnosis, and treatment over the past few decades. However, little is known about the occurrence of synchronous or methacronous tumors with other histogenesis in addition to GISTs. The aim of this study was to present a series of 15 patients diagnosed with a second primary neoplasm in addition to GIST. MATERIAL AND METHODS:Patients who were diagnosed with both GIST and other primary neoplasm between January 2010 and December 2019 were included in the study. Demographic, clinicopathologic and immunohistochemical parameters of the patients were analyzed along with the follow-up results RESULTS: This study included 12 men and 3 women with a median age of 68 years (range: 57-83 years). Of the GISTs, 93.3% were localized in the stomach and 73.3% were at very low / low risk category. Of the second primary tumors, 66.6% were in the gastrointestinal tract. Detection of the GIST was synchronous in 9 cases, metachronous in 2 cases and preceded the GIST diagnosis in 4 cases. GIST was incidentally found intra-operatively in 3 of the cases. The mean size of the synchronous GISTs was 20 mm while the most common GIST-associated malignancy was gastric adenocarcinoma. The median follow-up times was 62 months (range: 13-129 months). CONCLUSIONS:The prevalence of secondary malignancies in GIST patients is significantly higher than the healthy population. The high occurrence rate of additional primary tumors in GIST patients has focused the attention of surgeons on this problem. While it is not yet clear if there is a causal association or a common genetic mechanism for the concomitant occurrence of GIST with other malignancies, a closer surveillance of GIST patients is needed due to their proved increased prevalence of a second primary tumor especially during the first year after diagnosis. KEY WORDS:Gastrointestinal stromal tumor, Coexistence, Synchronous malignancy, Second neoplasm, Gastric adenocarcinoma.