Metastasis of breast carcinoma to a primary mucinous cystadenocarcinoma of the ovary

A case of a patient with breast cancer metastatic within the tumor stroma of a primary ovarian carcinoma is presented. This finding is to the best of our knowledge the first case reported. The encountered diagnostic problems are discussed. A distinct peroperative frozen section diagnosis on the large, cystic, partially necrotic ovarian mass was not possible because of sampling problems. A comparable immunohistochemical staining pattern of cells being CEA negative, OC-125 negative, and HMFG-1 positive was found in both the primary breast tumor and in the solid epithelial parts in the tumor stroma of the left-sided ovarian carcinoma, as well as in the stroma of the right ovary. Immunohistochemical findings in the left-sided epithelial cystic ovarian tumor showed, as expected, apical reactivity with antibodies directed against CEA, whereas OC-125 and HMFG-1 were negative. Ploidy analysis showed that the primary breast carcinoma and the stromal part of left ovarian malignancy had the same aneuploid stemlines (DNA index = 1.18). The epithelial lining of the cystic ovarium carcinoma not showing the presence of a metastatic lesion in its stroma showed the presence of a diploid GO,1 population only. These results show that DNA flow cytometry and immunohistochemistry may be helpful in assessing the origin of the malignancies in this unusual double presentation of both metastatic breast cancer and primary ovarian carcinoma.