Immature endodermal teratoma of the ovary: embryologic correlations and immunohistochemistry.

Two grade 2 ovarian immature, predominantly endodermal teratomas are reported. The teratomas were in stage I and occurred in two girls, 9 and 10 years of age, who were treated with triple chemotherapy. These neoplasms differed from the usual immature ovarian teratoma as they contained no neuroectodermal components and had high alpha-fetoprotein and low human chorionic gonadotropin levels as their serum markers despite the absence of other concomitant germ cell tumors. The epithelia of the teratomas demonstrated exclusively the embryologic development of endoderm, ranging from early endoderm to tissues similar to esophagus, liver, and intestinal structures. All epithelial derivatives were positive for alpha-fetoprotein and alpha 1-antitrypsin. Liver and esophagus expressed fibrinogen, while intestine and esophagus were positive not only for carcinoembryonic antigen and chromogranins but also for thyroglobulin, thus reflecting yet another type of endodermal differentiation into thyroid. Focal human chorionic gonadotropin positivity associated with primitive intestinal and esophageal epithelia may reflect the early embryologic relationships between endoderm and trophoblast. These cases demonstrate that simultaneous alpha-fetoprotein and human chorionic gonadotropin secretion may occur in immature teratoma. The mesenchymal component also showed a wide range of differentiation, from primitive mesoblastic cells to differentiated cells, such as hemopoietic foci, smooth muscle, bone, and cartilage. Both the primitive endoderm and the mesenchyme co-expressed vimentin and keratin, reflecting their intimate developmental relationships and possibly supporting the hypothesis of mesenchyme originating from endoderm, as suggested by previous embryologic studies. Since endodermal and mesenchymal areas similar to those described here are found in association with yolk sac tumors and embryonal carcinoma, it is possible that the present cases may represent an endodermal differentiation accomplished by either of these developmentally related germ cell tumors.