Incidental Gastrointestinal Stromal Tumors – What can we learn from them?

Abstract

Abstract Introduction/Objective Gastrointestinal stromal tumors (GIST), albeit very rare overall, with approximately 5,000 new diagnoses yearly in the US, represent the most common mesenchymal tumor involving the GI tract. particularly the stomach and small bowel. Much progress has been made in the past two decades in terms of classification and targeted therapy of GIST, however, their behavior is still quite challenging and unpredictable, and their prognosis remains guarded. Methods/Case Report We reviewed our institutional experience with GIST over the past decade and identified 80 GIST in total, 5 of which were incidental findings, meaning that they were detected as a secondary diagnosis in a specimen that was obtained for a different pathology. All 5 tumors were less than 2 cm in greatest dimension and showed less than 5 mitoses/ 50HPF, which put them into the “no risk of malignant progression category”. As a matter of fact, all five tumors were less than 1 cm (ranging from 0.2-0.7cm), while the mean size overall for GIST is 6 cm, ranging from 0.2-40 cm. They were all c-kit and DOG-1 positive, and 3 out of 5 incidental GIST were diagnosed in association with an adenocarcinoma of the GI tract (gastric or distal esophagus). Three of the 5 incidental GIST were located in the stomach, one in the distal esophagus and one in the sigmoid; unsurprisingly, two gastric and one esophageal GIST were associated with poorly differentiated adenocarcinoma of the stomach or distal esophagus. The mean age at diagnosis in our series was 72.4 yo, while reported mean age for GIST ranges between 60-65yo. All but one of the patients with incidental GIST were males, while there seems to be no gender predilection in GIST in general. The two benign cases associated with incidental, “no risk” GIST were perforated diverticulitis and sleeve gastrectomy for morbid obesity. Review of the stained slides showed no apparent increase of interstitial cells of Cajal in the blocks containing the tumor. Results (if a Case Study enter NA) NA Conclusion In summary, we report a small series of 5 incidental GIST diagnosed over a span of 10 years in our institution. Although a rare tumor overall, with an annual incidence of 10-20 new cases/ million, incidental GIST is even more rare, in our case representing 6.25% out of the total number of cases diagnosed in a decade. Increased awareness of the incidental GIST and closer pathological assessment may throw more light into the pathogenesis of GIST in general.