S3393 Granular Cell Tumor of the Colon - Surprise Beneath the Mucosa!

Abstract

INTRODUCTION: Granular Cell Tumors (GCT) are a rare soft tissue neoplasm that arise from Schwann cells. Even though these tumors are generally benign, 1-2% of the cases have been reported to be malignant. Although usually found in the oral cavity or subcutaneous tissue, 8% of cases manifest in the gastrointestinal (GI) tract. In those patients, the esophagus is the most frequently affected organ, followed by the duodenum, anus, stomach. The least common sites are the colon and rectum. To date ∼ 150 cases of Colonic GCT have been reported in the English literature. Most GCT tend to be asymptomatic and less than 2cm in size, hence they are usually discovered incidentally during routine colonoscopy or abdominal imaging. Herein we report a unique case of GCT of the ascending colon measuring 11mm in size in a patient presenting with constipation that was treated successfully with endoscopic resection. CASE DESCRIPTION/METHODS: A 55-year old male with a history of external hemorrhoids presented to the GI clinic with constipation for two weeks. His previous colonoscopy eight months prior revealed a one cm polyp in the ascending colon, but it was not removed due to poor preparation. Repeat Colonoscopy revealed an 11 mm semi pedunculated polyp in the ascending colon. The polyp was removed with hot snare polypectomy followed by the placement of hemostatic clips. (Figure#1). Histopathologic examination of the resected polyp showed an intramucosal and submucosal tumor composed of polygonal cells with abundant amphophilic granular cytoplasm and centrally or eccentrically located small round or irregularly shaped nuclei (Figure#2). Margins of the resected polyp were free of tumor. Immunohistochemical analysis showed tumor cells were positive for S100 (Figure#3), CD68, and inhibin and negative for CD117 and neurofilament. On the basis of the above findings, the tumor was diagnosed as GCT. He followed up with a gastroenterologist as an outpatient one month later and had reported no symptoms. DISCUSSION: Colonic GCT are usually discovered at the time of colonoscopy as small, sessile, yellowish-white nodules or polyps covered by normal-appearing mucosa. Definitive diagnosis can be made by histopathology and immunohistochemical analysis. Endoscopic removal is the safest and most effective treatment. Though typically benign, gastroenterologists should be aware of malignant features such as a size greater than 4cm or rapid growth. It is important to consider GCT when one encounters a subepithelial lesion during colonoscopy.Figure 1.: A-11mm semi-pedunculated polyp in the ascending colon B-Prophylactic application of resolution clip at the polyp removal site.Figure 2.: The morphology of granular cell tumor in intramucosal and focally submucosal location in a colon polyp (H&E: 10x). Infiltrative growth pattern with nested or trabecular cellular clusters or sheets are appreciated. The cells are with abundant amphophilic granular cytoplasm and centrally or eccentrically located small round or irregularly shaped nuclei. No necrosis or mitosis is appreciated.Figure 3.: S100 positive staining highlighted the infiltrating trabecular growth pattern of this granular cell tumor (H&E: 10x).