ERBB2 and breast cancer: In contrast, PALB2 mutation carriers were more likely to have ER−HER2− breast cancer (46% in mutation carriers vs. 14% in non-carriers, p = 0.006) and less likely to have ER+HER2− breast cancer (31% in mutation carriers vs. 62% in non-carriers, p = 0.04) compared to mutation-negative women.