To take a deeper look in the biological relevance of NDRG2 regarding the heterogeneous nature of breast cancer, we initially analysed mRNA expression in 45 subtype-classified breast tumors, including triple negative (n = 28), HER2-enriched (n = 4), luminal A (n = 7), luminal B (n = 4) breast cancer specimens, and 15 normal breast tissues by real-time PCR. The gene discussed is ERBB2; the disease is breast cancer.