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Metastasizing breast carcinoma to the brain: a clinicopathologic and immunohistochemical study of 14 matched pairs.

Brain metastasizing breast cancer is the second most common cause of brain metastases. The frequency of brain metastasis ranges between 10‐40% of breast cancers. Hormonal status of the primary malignancy is thought to play a role in determining which tumors eventually will show brain metastasis. In this study, we examined 14 pairs of matched primary breast carcinomas and their respective brain metastases for various clinicopathologic parameters and performed immunohistochemical staining for estrogen receptor (ER), progesterone receptor (PR), Her‐2/neu, and epidermal growth factor receptor (EGFR). The mean age at diagnosis of breast primary and the subsequent brain metastases was 54.8years (36–74) and 57.7years (39–75), respectively. The mean interval between the diagnosis of breast carcinoma and the brain metastasis was 32 months (4 months–8 years). All 14 breast primary cancers were of the invasive ductal type and over half (8/14) were high grade (SBR III/III). Nine (64%) of the matched pairs were ER negative and 10 (71%) were PR negative but only 7 (50%) were both ER/PR negative. Three (21%) pairs were found to be Her2/neu positive by immunohistochemistry. Overall, 5 (36%) matched pairs were “triple negative”. Diffuse and strong EGFR immunoreactivity was observed in 4 primary breast cancers and only 2 brain metastases. Both EGFR positive brain metastases had EGFR positive primaries. EGFR‐ positive pairs were more frequently “triple negative” or in one case, ER/PR negative and Her2/neu positive. Her2/neu analysis by FISH is underway.