The TIMER database showed that MCT4 expression was associated with dendritic cell infiltration in all breast cancer patients (correlation = 0.351) and the basal-like subtype (correlation = 0.316), and macrophage and B-cell infiltration in the HER2+ subtype correlated with MCT4 expression (correlation coefficients of 0.328 and −0.385, respectively) [26]. This evidence concerns the gene ERBB2 and breast cancer.