A case of mucoid carcinoma of the sigmoid colon with features of a submucosal tumor.

An 82-year-old man visited a medical clinic for dyschezia. His serum carcinoembryonic antigen (CEA) level was 16ng/ml. Abdominal computed tomography (CT) revealed an 8×7cm tumor in the sigmoid colon. Endoscopy showed that the sigmoid colon was insufficiently dilated but no mucosal lesions were present. Histological examination of biopsy specimens did not show malignant cells. Sigmoidectomy was performed due to suspected submucosal tumor. The final pathological diagnosis was mucoid carcinoma with features of a submucosal tumor which had no mucosal lesions. Mucoid carcinoma with features of a submucosal tumor in the colorectum is rare. Most cases are associated with ulcer lesions or scar lesions on the mucosal surface of tumor because it arises from epithelial cells.