Granular Cell Tumor of Colon (GCT)

Abstract

Purpose: We report a case of GCT in the sigmoid colon. A 58 year-old male patient underwent a screening colonoscopy where a yellowish, sessile submucosal nodule about 1 cm in diameter was found in the sigmoid colon. A complete endoscopic snare resection was performed without complications. Histology revealed the tumor consist of plump neoplastic cells with abundant granular eosinophilic cytoplasm containing acidophilic periodic acid Schiff positive, diastase-resistant granules. Immunohistochemical analysis showed the tumor cells expressed S-100 protein and neuron-specific enolase, characeristics of GCT. GCT is a relatively rare soft tissue tumor that can be located anywhere in the body. It commonly occurs in oral cavities and subcutaneous tissue but is uncommon in the colon and rectum. In the GI tract the most common site for GCT is the esophagus, followed by the duodenum, anus and stomach. This benign tumor appears as a submucosal nodule, usually less than 2 cm in diameter, and is often found incidentally during screening colonoscopy. The final diagnosis of GCT is based on histology. DISCUSSION In our case, the endoscopic features of the tumor resembled a simple sessile polyp. Interestingly, our patient had a screening colonoscopy three years ago and at that time this nodule was noted to be 6 mm in size, and was incompletely removed with a cold biopsy forceps. We performed one-stage endoscopic complete snare polypectomy during repeat colonoscopy. Although GCTs are usually benign, some malignant cases have been reported. Malignancy correlates with tumor size; more than 60% of metastatic GCTs were larger than 4 cm in diameter. To date no cases of malignant colonic GCT have been described. In most colonic GCTs, the tumor size is less than 2 cm and confined to submucosa. The endoscopic removal has been advocated as the most appropriate choice of treatment, however, incomplete removal may result in regrowth of the lesion. Colonoscopists should consider the possibility of GCT in the differential diagnosis of submucosal tumors of the colon.Figure: Tumor cells with round to spindled nuclei and abundant granular eosinophilic cytoplasm.