Invasive micropapillary carcinoma of the extrahepatic bile duct and its malignant potential.

Invasive micropapillary carcinoma (IMPC) was originally described as a distinctive type of invasive carcinoma in the breast, but it has not been recognized as a histological type of the extrahepatic bile duct cancer. The present study demonstrated clinicopathological features and patient prognosis of IMPC. We examined histological reviews of 93 consecutive cases of the extrahepatic bile duct cancer and identified 13 cases which included IMPC component. The component of IMPC ranged from 5 to 60% of the primary tumor tissue, which was mainly detected at the invasive front of the tumor. Of the 13 cases, 12 (92.3%) carcinomas with IMPC showed lymph node metastasis more frequently compared to conventional adenocarcinoma (39.2%, P<0.001). Presence of IMPC component was significantly associated with poor overall survival (P=0.003). In conclusion, extrahepatic bile duct carcinoma with IMPC component showed significant lymphatic invasion, lymph node metastasis, and resulted in poor prognosis.