Taking into account the histopathological features of clinical samples, plasma miR-21 levels were upregulated in luminal B and Her-2+ types of breast cancers compared with luminal A and basal-like types, which indicates that miR-21 levels might be related to estrogen receptor (ER) and Her-2 status in breast cancer (Fig. 1e). The gene discussed is ESR1; the disease is breast cancer.