We have recently shown that the notoriously low take rates of ER+ BC xenografts of both cell lines and patient‐derived tumor cells can be markedly improved by grafting the cells to the milk ducts of immunocompromised mice (Sflomos et al, 2016), a finding that extends to androgen receptor‐positive, molecular apocrine BCs (Farmer et al, 2005; Richard et al, 2016). The gene discussed is ESR1; the disease is neoplasm.