This is a case of a cystic breast metastasis to the brain. The patient underwent excision of the right frontal lesion. Intraoperative histopathology revealed reactive cerebral tissue and metastatic carcinoma. Immunohistochemistry demonstrates that the tumor was positive for Cam-5.2 and MNF-116, with focal staining for CDX-2 and Mucin, and with small numbers of tumor cells stained with GATA-3, Mammaglobin and S-100. The tumor was negative for ER (estrogen receptor), PR (progesterone receptor), TTF-1, P40, and Syn. These findings were suggestive of a poorly differentiated adenocarcinoma, though the exact primary was uncertain.

Additional immunohistochemical staining showed SOX-10, but negative for AR (androgen receptor) and HER-2. On further review, the initial staining profile and morphology from the breast lumpectomy (resected ~10 years prior) was similar to the metastatic lesion, compatible with triple-negative breast ductal carcinoma to the brain.

The patient initially declined chemotherapy and radiation, but eventually accepted palliative whole brain radiation therapy and capecitabine.

Co-authors:
Ekaterina Sazon