Pure Micropapillary Rectal Carcinoma with CK7 and CK20 Coexpression and Loss of CDX2 Reactivity

The micropapillary carcinoma is regarded as an aggressive variant of adenocarcinoma in any location. Histologically is characterized by papillary cell clusters surrounded by clear spaces. The reported proportion of micropapillary carcinoma component to the entire tumor ranged from 5 to 80% and no pure cases has been reported. There are near of 130 cases reported to date in colorectum. We experienced a patient with a pure micropapillary carcinoma showing coexpression of CK7, CK20, and absence of CDX2, which had an aggressive neoplasm with extense perineural, vascular and lymphatic invasion also extensive nodal metastasis. The presence of a micropapillary carcinoma in the colorectum seemed to be closely related with nodal metastasis, similar to the case for micropapillary carcinomas in other organs. Therefore, if a micropapillary component is identified in a tumor, particularly in a biopsy specimen, even if the pre-operative diagnosis is a pedunculated early colorectal cancer, should be carefully consider the extent of surgical resection due to the high potential for nodal metastasis.