Spindle Cell Carcinoma of the Common Bile Duct: Case Report with Immunohistochemical Analysis

The author reports a very rare case of spindle cell carcinoma of the common bile duct with an emphasis on immunohistochemical features. A 65-year-old man was admitted to our hospital because of jaundice. Imaging modalities revealed a tumor of the common bile duct, and bile cytology demonstrated malignant cells. A pancreatico-duodenectomy was performed. Grossly, an elevated tumor (15 × 10 × 3 mm) was present in the middle portion of the common bile duct. Microscopically, the tumor consisted of well-differentiated adenocarcinoma (20% in area) and spindle cell carcinoma (80% in area). There were gradual transitions between the two. The tumor cells invaded into the serosa. Immunohistochemically, the spindle cell carcinoma element was positive for four types of pancytokeratins, cytokeratin 7 (CK7), CK8, CK18, CK19, CK20, epithelial membrane antigen, vimentin, p53 protein, Ki-67 (labeling = 52%), and CEA. It was negative for high-molecular-weight CK, CK5/6, CK14, p63, neuron-specific enolase chromogranin, synaptophysin, CD56, CA19-9, CD34, desmin, S100 protein, myoglobin, a-smooth muscle antigen, CD34, CD68 and KIT. The adenocarcinoma element showed similar immunoreactivity except for negative vimentin, and positive CA19-9. The present case is the first report of spindle cell carcinoma of the common bile duct demonstrating an extensive immunohistochemistry. The spindle cell carcinoma in the present case may be derived from sarcomatous transformation of the adenocarcinoma element. CK20 newly emerges in the development of spindle cell carcinoma of the common bile duct.