Ovarian giant cell tumor with cystadenocarcinoma.

A 25-year-old woman had a malignant ovarian tumor with two distinct tumor patterns: pseudomucinous cystadenocarcinoma and malignant giant cell tumor of bone. One area of the tumor had a lining of tall columnar epithelium with abundant mucin production; however, another area of the same tumor had a number of large multinucleated giant cells that resembled osteoclasts, intermingled with mononuclear stromal cells. There was no blending of the two tumor patterns. Mitoses were frequent in both areas. A probable histogenesis of the tumor from a malignant teratoma is suggested.