ARID1A and neoplasm: Among the 341 genes for which all samples were sequenced, the most commonly altered genes across all primary tumor and BrM samples were TP53 (41 [80.4%]), CDKN2A (16 [31.4%]), ERBB2 (15 [29.4%]), SMAD4 (11 [21.6%]), and PTRPT (11 [21.6%]); alterations in ARID1A were present in 9 samples (17.6%), EGFR in 9 samples (17.6%), ERBB3 in 8 samples (15.7%), ERBB4 in 9 samples (17.6%), and RARA in 8 samples (15.7%).