Intrahepatic sarcomatoid cholangiocarcinoma of round cell variant: a case report and immunohistochemical studies.

Sarcomatoid transformation was observed in 4.5% of autopsied cases of intrahepatic cholangiocarcinoma. Here, we report a case of intrahepatic sarcomatoid cholangiocarcinoma with round cell feature, extremely rare variant. An 87-year-old man was incidentally found to have a tumor in the left lobe of the liver by abdominal computed tomography scans. The patient was clinically diagnosed to have intrahepatic cholangiocarcinoma and received palliative care without specific treatment. He died of hepatic insufficiency 3 months after the diagnosis. The autopsied liver specimens showed a reddish gray tumor of 4.0x2.8 cm in size. Histologically, the tumor was centrally hemorrhagic and necrotic and was composed of tubular adenocarcinoma and a round cell component, which has an eccentrically located nucleus and eosinophilic cytoplasm without mucin production. Immunohistochemically, the adenocarcinoma cells expressed cytokeratin 19 and beta-catenin in their cytoplasm, with E-cadherin and CD44s at the plasma membrane. In the round cells, cytokeratin 19 and vimentin was detected in their cytoplasm and CD44s at the plasma membrane. E-cadherin immunoreactivity was weakly present in their cytoplasm and beta-catenin was negative. Loss or reduction of the E-cadherin and beta-catenin expressions and overexpression of CD44s in the round cells are suggested to be contributed to the high propensity for lymphatic permeation and poor prognosis.