Schwannoma of the colon presenting as a submucosal lesion: diagnostic challenge and surgical management

Schwannomas are rare benign nerve-sheath tumours that uncommonly involve the gastrointestinal tract, with the colon and rectum among the least frequent sites. We report a 36-year-old man with a 2-year history of central colicky abdominal pain, alternating bowel habits (predominantly constipation), intermittent rectal bleeding and bloating. Computed tomography (CT) and colonoscopy revealed a 2-cm submucosal lesion at 23 cm from the anal verge; endoscopic ultrasound showed a homogeneously hypoechoic, smooth-margined mass originating from the muscularis. The patient underwent laparoscopic anterior resection after endoscopic tattooing. Recovery was uneventful. Histopathology confirmed a 1.5-cm benign colonic schwannoma with clear margins and 17 negative lymph nodes. At follow-up he remained asymptomatic without recurrence. Colorectal schwannoma can mimic gastrointestinal stromal tumour or leiomyoma preoperatively; definitive diagnosis requires histology and immunohistochemistry (S100 positivity), and complete excision with negative margins is curative.