GASTROINTESTINAL STROMAL TUMOR IN THE EXCLUDED GASTRIC REMNANT AFTER ROUX-EN-Y GASTRIC BYPASS

Objectives:

Introduction: Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the GI tract. Despite this, they rarely occur, accounting for only 1% to 3% of all gastrointestinal tumors. GISTs are hypothesized to originate from the interstitial cells of Cajal, which regulate bowel motility and peristalsis through communication between the autonomic nervous system and the smooth muscle of the bowel [1]. The occurrence of gastric malignancies is extremely rare after bariatric surgery, with the majority of these being adenocarcinomas and only a minority GISTs. There are currently only 3 known reported cases of GISTs after Roux-En-Y gastric bypass surgery (RYGB).

Case Presentation: A 53-year-old female presented to the clinic with fatigue and right upper quadrant abdominal pain. Surgical history was notable for prior RYGB 13 years prior, cholecystectomy, and total abdominal hysterectomy.
Abdominal ultrasound revealed a large, conglomerate mass. CT imaging revealed a large heterogeneous mass (20 x 12 x 16 cm) at the gastrosplenic region which was inseparable from the excluded stomach remnant (See Figure 1). Ultrasound guided biopsy proved the mass to be a GIST.
The initial attempt at surgical intervention at an outside facility was deemed unresectable secondary to extensive infiltration of the mass inferiorly towards the celiac vessels and superiorly towards the gastroesophageal junction. After neoadjuvant Gleevec with minimal response, the patient was then referred to surgical oncology for resection. Patient underwent an exploratory laparotomy with distal pancreatectomy, partial colectomy, partial gastrectomy, and splenectomy. Intraoperatively, a large mass originated from the greater curve of the excluded stomach remnant post gastric bypass with involvement of the spleen, lateral segment of the liver, tail of the pancreas, as well as the transverse mesocolon. The resected specimen measured 16 x 16 x 8.0 cm.
Pathology revealed tumor cells that were c-kit positive and of the spindle cell subtype which are findings consistent with GIST. All margins were negative. Postoperatively, the patient had a uncomplicated inpatient course and has had no recurrence of disease on follow up visits. She was treated with Gleevec post-operatively.

Discussion: GISTs are extremely rare findings in bariatric surgery patients. Previous studies have identified GISTs in post-op bariatric patients, though these were either c-kit negative tumors, or after bariatric surgery other than RYGB [2, 3, 4]. Our case deemed significant as it presents as one of the few c-kit + GIST arising from the excluded stomach remnant post RYGB to be described in literature.

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