JUVENILE GRANULOSA-CELL TUMOR OF THE TESTIS - A COMPARATIVE IMMUNOHISTOCHEMICAL STUDY WITH NORMAL INFANTILE GONADS

This study concerns the nature of two different cell populations in a juvenile granulosa cell tumor (GCT) of the infantile testis. Immunohis tochemical features of the tumor were compared with those Of normal in fantile testes (six cases) and ovaries (six cases). The testicular neo plasm showed follicles, cysts and solid nodules composed of an interna l layer of polyhedral cells that expressed cytokeratin and vimentin. M ost of the follicles and nodules were surrounded by an external layer of spindle cells that reacted to muscle-specific actin, vimentin, and focally to desmin. A neoplastic rather than reactive origin of the spi ndle cell population is favored by their concentric arrangement in a p eritubular-like or theca-like fashion and by their immunohistochemical correlation with normal peritubular-myoid and theca externa cells. Se rtoli and granulosa cells of normal infantile gonads were positive for cytokeratin and vimentin; peritubular myoid and theca externa cells e xpressed muscle-specific actin, vimentin, and focally desmin. The occu rrence of two well-differentiated components in the tumor favors its o rigin from the primitive specialized gonadal stromal cell that during neoplastic transformation develops bidirectional differentiation towar d epithelial-like and smooth muscle-like lineages. The possibility tha t this tumor is composed of immature Sertoli and peritubular myoid cel ls is discussed.