A Coincidental or Connected: Synchronous Giant Gastric GIST and Malignant Colonic Polyp: A Case Report

Synchronous Giant Gastric GIST and Malignant Colonic Polyp

Abstract

Introduction and importance : Gastrointestinal Stromal Tumors (GIST) are rare mesenchymal neoplasms of the gastrointestinal tract, most commonly occurring in the stomach. The concurrence of GIST with another malignancy is an uncommon phenomenon, with few works of literature reported. We report a rare synchronous giant gastric GIST with a malignant colonic polyp.

Case Presentation: A 70-year-old woman presented with an upper abdominal mass. There was no change in bowel habits. CEA level was normal. Contrasted computed tomography (CT) of the abdomen revealed a huge gastric mass with incidental finding of suspicious mass at sigmoid colon . Oesophagogastroduodenoscopy (OGDS) revealed extrinsic compression with normal overlying mucosa, suggesting that the mass is submucosal. Colonoscopy showed a large polypoidal mass in the sigmoid colon, which initialy biopsy revealed tubulovillous adenoma with high-grade dysplasia. Wide local excision of gastric tumour and on table snare polypectomy was performed. The base of polyp was also taken for biopsy. The patient had an uneventful recovery and was discharged home well. Post operative histopathological examination showed Gastric Gist and Adenocarcinoma of sigmoid polyp. The base of polyp showed no malignancy. The patient was started on Glivec® 400mg OD.

Discussion: Gastrointestinal stromal tumours (GIST) and colon malignant polyps are two distinct types of neoplasms that can occur synchronously. GIST tumours arise from the interstitial cells of Cajal and are characterized by mutations in the KIT/PDGFRA genes. Conversely, malignant polyps are epithelial tumours that arise from the colonic mucosa classically due to alterations in the APC tumour suppressor gene, resulting in the overactivation of the WNT/ β-catenin signalling pathway.

Conclusion: Synchronous GISTs and malignant colon polyps are rare, and their molecular basis is distinct. However, it is crucial to consider the possibility of a genetic predisposition in patients with these tumors. In a case of GIST, the surgeon should recognize the possibility of another tumor with different histological origin. High clinical analysis needed during laparotomy for GIST to detect a synchronous tumor. Due to its rare occurrence and limited literature further studies has to be done on GIST with another synchronous tumor to help the surgeon to manage the patient optimally.