Even after accounting for tumor stage and other demographic characteristics, certain histological subtypes (eg, small-cell lung cancers and ductal breast cancers) and tumors with specific biomarkers (eg, triple-negative and HR-/HER2+ breast cancers) were more likely to metastasize to the brain.7,8,24–26 Identifying high-risk subpopulations may help inform strategies to promote early detection of IMD. This evidence concerns the gene ERBB2 and breast cancer.