Spindle and giant cell type undifferentiated carcinoma arising in the common bile duct: a case report.

We report on a 61-year-old Japanese male with a pedunculated tumor in the common bile duct. The tumor consisted of two types of neoplastic cells. The majority showed atypical spindle- and giant-shaped features and proliferated densely in an inflammatory stroma, revealing a sarcomatous pattern. They expressed vimentin, KL-1, and CAM5.2. The remaining minority showed glandular and tubular features, occupied only less than 5%, located only in the tumor surface, and expressed wide spectrum keratin, KL-1, CAM5.2, epithelial membrane antigen, AE1/AE3, and carcinoembryonic antigen. CD68-positive osteoclast-like giant cells were also observed. Therefore, the patient was diagnosed as having an undifferentiated carcinoma, spindle and giant cell type.