S3726 A Case of Schwann Cell Hamartoma Identified on Colon Polypectomy

Introduction: We report an interesting case of a patient with incidental finding of Schwann cell hamartoma following removal of a colon polyp. Case Description/Methods: A 62-year-old woman presents for screening colonoscopy following ventral hernia repair for iron deficiency anemia with concern for chronic blood loss. Previous colonoscopy was incomplete due to looping of the colonoscope in a hernia sac. Family history is negative for colon cancer. Blood count reveals hemoglobin 10.2 g/dL, hematocrit 31.1%, iron 68 ug/dL, iron binding 242 ug/dL, iron saturation 28% and ferritin 179 ng/mL. computed tomography (CT) with IV contrast performed prior to hernia repair surgery shows presence of a short segment of the transverse colon within ventral abdominal wall hernia. The patient undergoes colonoscopy which shows a few small mouthed diverticula located in the sigmoid colon, small internal hemorrhoids, and a 5 mm, sessile sigmoid polyp is completely removed using a cold snare and sent for pathology. Pathology reveals colonic mucosa with ill defined islands and sheets of bland spindle cells extending to submucosa. Spindle cells stained positive for S100 and negative for actin and epithelial membrane antigen (EMA). Glucose transporter protein 1 (Glut-1) was positive in the upper mucosa. Findings were consistent with diagnosis of Schwann cell hamartoma. Patient was advised to repeat colonoscopy in 5 years for surveillance. Most recent iron studies reveal improvement with an increase in iron 93 ug/dL, iron saturation 41% and ferritin 234 ng/mL. Discussion: Schwann cell hamartomas are rare findings in the colon with pathology revealing islands with poorly delineated margins and bland spindle cells extending to the submucosa. Immunohistochemistry is positive for S100 and confirms the neuronal origin, and negative EMA and actin stain rules out epithelial and smooth muscle origin. The distinction is critical due to common GI manifestations of neurofibromatosis type 1 associated with neurofibromas and leiomyomas, in addition to neuromas or ganglioneuromas which present with a heterogeneous cellular composition. Schwann cell hamartomas are benign, lack association with inherited syndromes and do not require treatment beyond excision.