Cholangiocarcinoma (bile duct carcinoma)

Cholangiocarcinoma is much less common than HCC and not associated with cirrhosis. It arises from intrahepatic and extrahepatic bile ducts. The diagnosis can be made by bile cytology, brush cytology or percutaneous FNA.

Cytologic diagnostic features

• Isolated cells, crowded sheets and cell clusters, some in acinar arrangements
• Nuclear enlargement and pleomorphism
• Scanty cytoplasm
• Benign hepatocytes

Differential diagnosis

• Hepatocellular carcinoma
• Metastatic adenocarcinoma

The sinusoidal capillaries surrounding groups of tumor cells, typical of HCC, are not seen in cholangiocarcinoma, whose cells are cuboidal or columnar rather than polygonal as in HCC. Cholangiocarcinoma is a gland-forming tumor and mucin may be abundant. Positive staining for mucicarmine is very uncommon for HCC, and so is diffuse staining for CEA. The distinction between cholangiocarcinoma and metastatic adenocarcinoma is virtually impossible by cytology and immunocytochemistry and mainly rests on clinical history by ruling out other primary sites.