Clinicopathologic and Genomic Landscape of Breast Carcinoma Brain Metastases

Background Among patients with breast carcinoma who have metastatic disease, 15%–30% will eventually develop brain metastases. We examined the genomic landscape of a large cohort of patients with breast carcinoma brain metastases (BCBMs) and compared it with a cohort of patients with primary breast carcinomas (BCs). Material and Methods We retrospectively analyzed 733 BCBMs tested with comprehensive genomic profiling (CGP) and compared them with 10,772 primary breast carcinomas (not‐paired) specimens. For a subset of 16 triple‐negative breast carcinoma (TNBC)–brain metastasis samples, programmed death‐ligand 1 (PD‐L1) immunohistochemistry (IHC) was performed concurrently. Results A total of 733 consecutive BCBMs were analyzed. Compared with primary BCs, BCBMs were enriched for genomic alterations in TP53 (72.0%, 528/733), ERBB2 (25.6%, 188/733), RAD21 (14.1%, 103/733), NF1 (9.0%, 66/733), BRCA1 (7.8%, 57/733), and ESR1 (6.3%,46/733) (p