Coincidental Detection of Gastrointestinal Stromal Tumors During Laparoscopic Bariatric Procedures-Data and Treatment Strategy of a German Reference Center

Introduction Intraoperative pathologic findings during bariatric surgery are relatively rare. Gastrointestinal stromal tumors (GISTs) are commonly located in the stomach and account for <1% of all neoplasms of the alimentary tract. Coincidental detection of GISTs during bariatric surgery has been reported around 0.8%. We analyzed the incidence of GISTs in bariatric patients and investigated whether simultaneous resection can be oncologically adequate. Material/Methods A single-center retrospective study of 707 morbidly obese patients, who underwent bariatric surgery (either Roux-en-Y gastric bypass (RYGB), One Anastomosis Gastric Bypass (OAGB), or sleeve resection (LSG) between January 2012 and August 2018). Intraoperative incidental GISTs were recorded and documented for tumor size, localization, immunoreactivity, and mitotic index. Results Nine (1.27%) patients were identified with GISTs. Seven (78%) tumors were detected in women; mean age 55.6 (range 27-74), mean BMI 51.7mg/m2 (range 38-71). GISTs were predominantly located in the stomach (78%) and two (22%) within the small bowel; six were found during RYGB vs. three during LSG. No abort of surgery or change of the intended procedure was necessary. All tumors (0.2-3.7 cm) were resected with disease-free surgical margins and displayed low malignancy. No adjuvant therapy was necessary. Conclusions The incidence of incidental GISTs in our series was higher to what has already been reported. Risk of malignancy was low and resection as part of the bariatric procedure was considered as definitive treatment. Suspicious tumors should be removed and confirmed by histology. In case of GIST histology, tumor resection with negative margins may be weighed as complete oncological treatment if there is low risk of malignancy.