New and unusual aspects of ovarian germ cell tumors.

Ovarian germ cell tumors are reviewed with emphasis on recent developments. In the primitive germ cell tumor group the recently recognized subtypes of yolk sac tumor, the hepatoid and glandular variants are described. Hepatoid tumors, which resemble hepatocellular carcinomas, are usually admixed with other patterns of yolk sac neoplasia but when the hepatoid component predominates, distinction from metastatic hepatocellular carcinoma may be difficult. Glandular yolk sac tumors include those with a cribriform pattern as well as tumors that may be confused with endometrioid carcinoma. Within the teratoma category, a recent paper exploring the occasional relation between immature teratomas and dermoid cysts is reviewed. Problems caused by some of the monodermal teratomas are also highlighted. Struma ovarii may be the source of many diagnostic problems. It may be cystic and microscopic examination may reveal inconspicuous numbers of clearly recognizable thyroid follicles, resulting in confusion with other cystic ovarian tumors. In noncystic strumas many patterns, such as solid or pseudotubular, may be seen and the presence of cells with abundant clear or eosinophilic cytoplasm may add to the diagnostic difficulty, particularly if other teratomatous elements are lacking. Immunohistochemical staining for thyroglobulin may be crucial in establishing the diagnosis of a struma in these situations. The problem of identifying reliable criteria for malignancy of struma ovarii is explored on the basis of recent information. The two most recently recognized subtypes of carcinoid tumor, strumal and mucinous, are reviewed as are primary neuroectodermal and sebaceous tumors of the ovary. Unusual clinical features of germ cell tumors are discussed under three main categories: endocrine syndromes, paraendocrine and paraneoplastic syndromes, and miscellaneous. Included in these categories are disorders such as sexual precocity in association with germ cell tumors containing syncytiotrophoblast cells, endocrine abnormalities associated with the recently described functioning ovarian tumors with peripheral steroid cell proliferation, hyperthyroidism with struma ovarii, the carcinoid syndrome, autoimmune hemolytic anemia associated with dermoid cysts, complications of dermoid cyst rupture, which may simulate disseminated carcinomatosis, and ascites and Meigs' syndrome associated with struma ovarii.