Molecular subtype of the primary tumor influences BrM likelihood, as seen in ALK-rearranged and KRAS-mutated non-small cell lung cancer (NSCLC) [8], or human epidermal growth factor receptor (HER) 2-positive and triple-negative breast cancer (TNBC) subtypes, which manifest earlier metastasis compared to estrogen receptor-positive (ER+) tumors [9–12]. The gene discussed is ESR1; the disease is neoplasm.