ABSTRACT
Plexiform neurofibroma (PN) is an uncommon benign tumor, usually associated with neurofibromatosis type 1. As most PNs involve the craniomaxillofacial region, PN of the colon is very rare. Here we present a case of PN involving the sigmoid colon. A 43-year-old male patient presented to the outpatient clinic for the evaluation of an incidentally discovered sigmoid colon mass. A colonoscopic biopsy was performed for the mass, and the result revealed neuronal proliferation. The patient visited the outpatient clinic a year later with symptoms of abdominal pain and stool caliber change. Biopsy was repeated for the sigmoid colon mass, and the results showed mucosal Schwann cell proliferation and S-100 immunostaining positivity. Computed tomography and magnetic resonance imaging were performed for further evaluation, and neurofibroma or schwannoma was suspected based on the imaging studies. For an accurate diagnosis, the patient underwent surgery to remove the sigmoid colon mass. The final diagnosis of the mass was confirmed as PN. We hereby report a rare case of PN involving the sigmoid colon that could not be diagnosed before surgery.