Colonic Mucosal Schwannoma

Abstract

Introduction: Neural lesions of the colon are a rare group of colorectal disorders that may frequently present as small polyps. Schwannomas represent a small percentage of GI mesenchymal tumors, and rarely occur in the colon. We report a case of a colorectal polyp in a female patient, detected during colonoscopy for work-up of rectal bleeding. Her colonoscopy revealed mucosal spindle cell proliferation consistent with Schwann cell hamartoma. Case report: A 37-year-old female with history of hypertension presented with an episode of rectal bleeding with mild lower abdominal discomfort. Patient had a family history of larynx cancer in father and brother, and breast cancer in paternal grandmother. She had history of rectal bleeding several years ago, when she was found to have tubule-villous adenoma on colonoscopy. The last follow-up colonoscopy, done about a year ago, showed seven 3-5 mm polyps in the sigmoid, descending, and ascending colon; biopsy revealed small polypoid colonic mucosa with benign spindle cell proliferation in the lamina propria, positive for S100. No ganglion cells were noted in the biopsies. The patient underwent colonoscopy this year, and was found to have six 3-4 mm polyps in the sigmoid, descending, transverse, and ascending colon, with biopsy revealing large bowel mucosa with superficial neuroid spindle cell proliferation, suggestive of mucosal schwann cell hamartoma with positive S 100, and retained PTEN. Discussion: The gastrointestinal tract schwannomas are rare, well-circumscribed, and non-encapsulated. These may be seen as polyps, intramucosal, or as transmural proliferation. These are more commonly seen in the stomach, and less commonly seen in the colon. Depending upon the location and size, schwannomas may cause bleeding, constipation, abdominal pain, or discomfort. Most of these tumors are slow-growing, and are incidentally found. Histologically all these polyps showed neuroid spindle cell proliferation, with positive S 100, PTEN suggestive of mucosal schwann cell hamartomas. These are considered benign in most cases, although they rarely become malignant. It is suggested that they should be excised completely. So far, there are no specific surveillance guidelines defined in the literature. Conclusion: Schwannomas in the gastrointestinal tract are benign and rare. Identifying them and making an accurate diagnosis is very important to distinguish from other colon polyp syndromes.