S4072 Mucosal Schwann Cell Hamartoma in the Transverse Colon: A Rare Finding and Location

Introduction: Mucosal Schwann cell hamartomas (MSCHs) in the gastrointestinal tract (GIT) are highly rare to the point that there is no data on its incidence and prevalence. Its prevalence has predominantly been demonstrated in the GIT via literature case reports. They are typically incidental findings during colonoscopy and are not associated with malignancy or inherited syndromes. Case Description/Methods: A 60-year-old African American woman with a history of paroxysmal atrial fibrillation, hypertension, and hyperlipidemia presented for a screening colonoscopy. She has a family history of colon cancer in her mother of unknown histology. She drinks alcohol socially and has never smoked tobacco. She has been compliant with her colonoscopy screenings with her last one being 5 years prior demonstrating benign polyps in the transverse colon and internal hemorrhoids. She presented with no new complaints. During this colonoscopy, a single 4 mm sessile transverse polyp was removed. The biopsy demonstrated the proliferation of bland spindle cells, positive for S100 and negative for CD68 and AE1/AE3, which was consistent with MSCH. She was counseled on the benign nature of the tumor and recommended to follow up with a repeat colonoscopy in 5 years. Discussion: MSCH is a rare, benign lesion that is asymptomatic when present. Although they are scarce in the GIT, when present they are detected as small polyps ranging from 1 to 8 mm and predominantly located in the rectosigmoid region. They are composed of bland spindle cells arranged in vague fascicles with S-100 positivity. At this time, there is no belief that MSCHs are related to inherited syndromes or malignancies. The differential diagnosis of these lesions is broad. This case demonstrates the importance of pathology to avoid mistaking it for gastrointestinal stromal tumors, colorectal neurofibromas, mucosal neuromas, gastrointestinal ganglioneuromas, gastrointestinal schwannomas, mucosal perineuromas, and inflammatory fibroid polyps.