Ovarian cystic tumor composed of Brenner tumor and struma ovarii

Ovarian tumor composed only of Brenner tumor and struma ovarii is very rare; only 6 cases have been reported in the English literature, to the best of the author's knowledge. A 66-year-old woman underwent right oophorectomy because of torsion of right ovarian cyst. Macroscopically, the ovarian cyst was hemorrhagic and red. Cystic content was hemorrhagic fluid. Microscopically, the cyst walls were composed only of Brenner tumor(50% in area) and struma ovarii(50% in area). Hemorrhage and ischemic changes were seen. Other elements were not recognized. No malignant transformation was noted. These two elements were separately present, and no mergers between them were recognized. Immunohistochemically, the Brenner tumor element was positive for cytokeratins(AE1/3 and CAM5.2) and Ki67(labeling=3%), but negative for thyroglobulin, TTF-1, p53, CA125, and vimentin. The struma ovarii element was positive for cytokeratins(AE1/3 and CAM5.2), thyroglobulin, TTF-1 and Ki67(labeling=5%), but negative for p53, CA125 and vimentin. The findings suggests that there were cases of ovarian cyst composed only of Brenner tumor and struma ovarii, that such a case may be monodermal mature cystic teratoma or the Brenner tumor element was derived from surface epithelium in the preexisting struma ovarii, and that such a tumor manifest as cystic torsion.