Bile duct-like differentiation in teratoma: a clinicopathologic and immunohistochemical study

The presence of biliary differentiation as part of teratoma is very unusual and has been reported only once as part of hepatocellular component; however, its incidence and significance were not studied. We reviewed available mixed germ cell tumors and pure teratomas for the last 18 years at our institution. Data on age, tumor size, location, gross and microscopic findings, proper prior clinical history, and outcome were obtained. Histologic components of teratoma were evaluated; percentage of bile duct-like structures was calculated, and cases were immunohistochemically studied. Forty-five cases were included (19 testicular neoplasms, 20 retroperitoneal lymph node resections, 5 mediastinal tumors, and 1 pulmonary resection), obtained from male patients 15 to 48 years old (mean, 28.8 years; median, 29 years). Bile duct-like tubules were identified in 11 (24%) cases. In 10 cases, the foci of bile duct-like structures represented less than 1% of the tumor tissue, whereas 1 case was almost exclusively composed of these structures. In all the cases, immunostains of bile duct-like tubules were positive for cytokeratin 7 and 19 and negative for other markers. Our findings show a significant prevalence of bile duct-like structures in teratoma. Immunohistochemical studies, although not specific, support a biliary-like immunophenotype. The presence of these structures did not adversely affect patient's prognosis; however, diagnostic awareness of their existence is relevant, as treatment and prognosis may vary significantly between teratomas and yolk sac or Sertoli cell tumors.