Fine structural evidence on the origin of gonadotropin-induced ovarian tumors in mice

A nonluteinized granulosa cell ovarian tumor and a purely luteinized ovarian tumor, induced by gonadotropin stimulation in mice, were studied ultrastructurally to obtain evidence concerning the possible origin of these tumors, whether from granulosa cells only or from granulosa and theca. Evidence including the presence of cells sharing features of both nonluteinized and luteinized cells, the presence of desmosomes and other junctional complexes in both cell types, and the presence of partially extracted lipid droplets in the luteinized cells suggests that the luteinized cells represent granulosa-lutein cells rather than theca-lutein cells. These findings are consistent with the concept that these tumors represent a spectrum of differentiation from nonluteinized granulosa cells to luteinized granulosa cells. The lack of theca and theca-lutein cells in both tumors implies that theca cells are not involved as progenitor cells.