On the other hand, recent DNA microarray profiling studies on breast tumors have identified five distinct subtypes of breast carcinomas [16,17,20–22]: Basal-like [triple-negative (ER−, PR−, HER-2−), CK5/6+ and/or HER-1+]; Basal-like/ luminal B (HER-2+, ER−, PR−); Luminal B (HER-2+, ER+ and/or PR+); Luminal A (HER-2− , ER+ and/or PR+); and unclassified subtype (tumors that are negative for ER, PR, HER-2, HER-1, and CK5/6). The gene discussed is KRT5; the disease is breast neoplasm.