Schwannoma of the Descending Colon

Abstract

A 75 year old male presented to a gastroenterologist for the work-up of an accidentally found descending colon mass. CT scan of the abdomen performed for evaluation of hematuria revealed non-obstructing 4.2 cm mass involving distal descending colon, highly suspicious for adenocarcinoma, small lymph nodes in adjacent mesentery and borderline enlarged retroperitoneal lymph nodes. Patient denied abdominal pain, change in bowel habits or hematochezia. His previous history included hypertension, atrial fibrillation and benign prostate hypertrophy. Previous colonoscopy was performed 7 years ago and did not reveal any lesions. There was no family history of benign or malignant tumors, or neurofibromatosis. Results of a physical examination of the abdomen and other systems were unremarkable. Laboratory tests (CBC, chemistry, LFTs) were within normal limits. During colonoscopy a large protruding mass was found in the distal descending colon, 40 cm from anal verge. It appeared submucosal with normal overlying mucosa, hard in consistency. [figure 1]Biopsy of the mass was unrevealing, except for melanosis coli. Resection of the left and sigmoid colon was performed with findings of 3.1×3.8 cm submucosal mass, well circumscribed, orange-tan in color, extending into serosal fat. Histology was consistent with cellular schwannoma. Immune stains confirmed the diagnosis (positive for S-100 protein; negative for CD117, CD34 and smooth muscle actin). Seven resected lymph nodes were without significant pathology. We reported a very unusual neoplasm of the colon. Schwannomas are mostly benign tumors deriving from the cells of Schwann that form the neural sheath. The gastrointestinal autonomic nerve tumors are uncommon stromal tumors, representing 2–6% of GIST, with most common location in the stomach and small intestine. Schwannomas of the colon are very rare. The diagnosis of GI schwannoma is difficult preoperatively; lesions appear as subepithelial tumors and biopsy specimens are likely to be normal. Immunochemical studies are required to distinguish schwannoma from other GIST. Surgical resection with wide margins is the cornerstone of treatment.Figure 1