Rectal granular-cell tumor difficult to distinguish from carcinoid tumor

A 60-year-old man had a positive fecal occult-blood test on a medical check-up. Colonoscopy revealed a yellowish-white submucosal tumor 8 mm in diameter in the rectum. Endoscopic ultrasonography showed a well-demarcated mass with a homogeneous, low-level, internal echo in the second to third layers of the rectal wall. A carcinoid tumor was suspected, and the mass was resected endoscopically. Histopathological examination revealed a granular-cell tumor. Gastrointestinal granular-cell tumors rarely arise in the rectum, and the preoperative diagnosis of small lesions is often difficult. In our patient, granular-cell tumor was difficult to differentially diagnose because the endoscopic and endoscopic ultrasonographic findings closely resembled those of carcinoid tumor. Interestingly, the endoscopic characteristics of the rectal granular-cell tumor in our patient resembled those of a carcinoid tumor.