[Invasive Micropapillary Carcinoma of the Colon That Was Difficult to Diagnose Preoperatively].

A 73-year-old man was admitted with sigmoid colon diverticulitis. Although a biopsy did not indicate malignancy, the sigmoid colon was completely obstructed following conservative treatment. After sigmoidectomy, the histopathological findings revealed a well-differentiated adenocarcinoma localized to the mucosal surface; invasive micropapillary carcinoma (IMPC)accounting for>95% of the tumor volume spread extensively below the submucosal layer. IMPC is highly malignant and difficult to diagnose preoperatively, possibly due to the presence of poorly differentiated histological sub-types in the deepest portions of the tumor.