The pathology of gonadal neoplasms composed of germ cells and sex cord stroma derivatives.

Neoplasms composed of germ cells and sex cord stroma derivatives intimately admixed together occur only in the gonads and consist of two distinctive and separate entities, gonadoblastoma and mixed germ cell-sex cord stroma tumour. These two entities differ from each other not only pathologically, but also in somatic, genetic, endocrine, and biological aspects. Gonadoblastoma which is the more common, occurs in young phenotypic females who are frequently virilized. The majority are chromatin negative and possess a Y chromosome. The gonad in which the tumour originates when not indeterminate is usually a streak or a testis. Gonadoblastoma is generally small and frequently bilateral. Histologically gonadoblastoma consists of cellular nests surrounded by connective tissue stroma. These nests usually show hyalinization and calcification, which may lead to the obliteration of the lesion. Gonadoblastoma is frequently overgrown by dysgerminoma and sometimes by other more malignant neoplastic germ cell elements. Mixed germ cell-sex cord stroma tumour occurs most frequently in somatically and genetically normal female infants and children in the first decade, and less frequently in anatomically normal elderly males. The tumours are unilateral and are usually large and solid. Histologically they are composed of germ cells and sex cord derivatives intimately admixed with each other forming a number of different patterns. There are no regressive changes and the tumour is actively proliferative. Admixture with other neoplastic germ cell elements is very rare, and metastases have never been encountered.