Breast carcinoma metastasis within granulosa cell tumor of the ovary: morphologic, immunohistologic, and molecular analyses of the two different tumor cell populations.

Gynecologic metastasis of breast carcinoma is not an infrequent event, but metastases within another tumor is very rare. We report a case of unilateral ovarian tumor arising in a 63-year-old woman receiving tamoxifen therapy with a past history of breast carcinoma. The microscopic appearance was principally that of a granulosa cell tumor, but the presence of atypical cells closely admixed within the classical areas was reminiscent of metastasis from breast carcinoma. The diagnosis of this first reported case of breast carcinoma metastasis within granulosa cell tumor was supported by immunohistologic analysis. The diagnosis of tumor-to-tumor metastasis was also confirmed by molecular study using microdissections of samples from the initial breast tumor and from the subsequent ovarian tumor. When compared with normal tissue, carcinomatous cells in the breast tissue exhibited genomic abnormality at the same locus as the metastatic cells in the ovary. In contrast, granulosa cell tumor areas did not show any loss of heterozygosity or instability for the microsatellites analyzed.