A higher rate of PD-L1 expression has been demonstrated in a subset of BCs with aggressive clinicopathological and immunohistochemical tumor features, such as grade 3 tumors, ER- and PR-negative tumors, or tumors with a Ki67 proliferation greater than 14%, and this is associated with a lower overall survival (OS) [23,24]. The gene discussed is ESR1; the disease is neoplasm.