Malignant mixed mullerian tumor of the ovary and bilateral breast cancer: an argument for BRCA3, or a coincidental cluster of unconnected cancers?

Malignant mixed mullerian tumors (MMMTs) of the ovary are a rare, aggressive subtype of ovarian cancer without a clear relationship to familial breast–ovarian cancer syndromes. We present the case of a woman with bilateral breast cancers who subsequently developed a stage IIIc MMMT of the ovary. The patient had a first-degree female relative with breast and ovarian cancer (not MMMT), as well as second- and third-degree female relatives each with bilateral breast cancers. BRCA1 and BRCA2 sequencing of germline DNA revealed no evidence of a heritable mutation. Ovarian MMMTs may be a hallmark of breast/ovarian cancer secondary to genetic risk independent of classic BRCA1/2 pathways.