Solitary polypoid ganglioneuroma of the sigmoid colon

We report the case of a 52-year-old man undergoing routine screening colonoscopy who was found to have a 3-cm submucosal mass in the sigmoid colon. Initial biopsy demonstrated S100 positivity, raising suspicion for ganglioneuroma (GN). Endoscopic ultrasound revealed a large hypoechoic submucosal lesion, and due to concern for possible gastrointestinal stromal tumor, size, and partial obstruction, the patient underwent partial colectomy. Surgical pathology confirmed a polypoid GN without atypia. Colonic GNs are rare, benign tumors derived from neural crest cells that may mimic other subepithelial lesions. Complete excision is typically curative, and though recurrence is uncommon, some experts advise follow-up imaging to monitor.