The frequency and histology of hepatic tissue in germ cell tumors.

The frequency of hepatic tissue and its histological characteristics were examined in 516 germ cell tumors. Hepatic tissue was observed in 48 cases (9.3%). The incidence of hepatic tissue was low in tumors of the ovary (5%), high in both retroperitoneal (27%) and sacro-coccygeal (24%) tumors, and low in both mature (0.3%) and immature teratomas (11%). It was usually encountered in infancy, and the frequency was high in both yolk sac tumors (48%) and mixed germ cell tumors (52%). The hepatic tissue found mainly in mature or immature grade 1 teratomas was similar to adult normal human liver tissue (Ha-type). Tissue in areas consisting of some immature somatic elements of a mixed germ cell tumor was similar to embryonic or fetal liver tissue (Hf-type). Many hepatic nests found in a polyembryoma were of both Ha- and Hf-types. The hepatic tissue found in close relation to yolk sac elements showed predominantly hepatocellular carcinoma-like features (HCLS). Immunohistochemically, the cytoplasm of adult liver-type cells was positive for alpha-1-antitrypsin (AAT), human albumin (ALB), and the third (C3) and fourth (C4) components of the complement system. The cytoplasm of fetal liver-type cells showed the same positivity; in addition, these cells were positive for alpha-fetoprotein (AFP) in 25% of the cases. The cytoplasm of hepatic cells of HCLS was positive for AFP, AAT, ALB, C3, and C4. A weakly positive reaction for CEA and CA19-9 was observed in bile duct-like structure in some Hf-type cases.