The ultrastructure of a feminizing granulosa-theca tumor.

A 13-year-old girl with evidence of hyperestrinism had a right ovarian tumor removed. This neoplasm was composed predominantly of granulosa cells and exhibited some changes of luteinization. The neoplastic cells displayed an investment of basement membrane material which was closely related to fibrillar collagen within the tumor. Scattered throughout the neoplasms were small numbers of cells with charcteristics of the theca and a few cells had cytoplasmic features suggestive of smooth muscle. The ultrastructural findings of eight similar tumors have been described. In none is the basement membrane material fully appreciated; nevertheless, the production of this extracellular material is a major and distinctive feature of granulosa-theca tumors.