We report a case of micropapillary carcinoma (MPC) of the transverse colon. A 56-year-old woman was admitted to our hospital with hematochezia. A lower gastrointestinal examination revealed an irregular ulcerative tumor of approximately 60 mm diameter with marginal elevation in the transverse colon. Abdominal computed tomography showed multiple swollen lymph nodes. A histological examination of the resected specimen revealed that cancer cells had invaded the subserosa. Microscopically, small papillary cells proliferated with lacuna spaces and the cribriform glandular configuration was observed. Immunohistochemically, the basal surface of the neoplastic cell clusters was diffusely positive for MUC1. No primary tumor was observed except for the colon. Therefore, this tumor was diagnosed as a primary MPC of the colon. Since a colorectal MPC was first reported in 2005, seven case reports and three pathological reviews have been presented in the English literature. MPC has an aggressive behavior with a high incidence of lymphovascular invasion and nodal metastases. We should take intensive chemotherapy for colorectal MPC into account, even if surgical resection is curative.
Keywords: Colorectal carcinoma; Lymph node metastasis; Micropapillary carcinoma.