Thecoma

Also known as theca cell tumor, this stroma-derived ovarian tumor contains lipid-rich cells resembling cells of the theca interna.  The cells have pale vacuolated cytoplasm and small oval nuclei. Also present, separating the lipid-rich theca cells, are spindle  cells as in a fibroma. Malignant thecomas can occur; 11% of 74 cases in one series.