Nine mRNAs were significantly differentiated in breast cancer sections, regardless of subtype, compared to the control samples: HRH1, HRH2, HRH4, histamine N-methyltransferase (HNMT), 5-hydroxytryptamine receptor 6 (HTR6), endothelin 1 (EDN1), endothelin receptor type A (EDNRA), adenosine deaminase (ADA), solute carrier family 22 member 3 (SLC3A2). The gene discussed is HRH4; the disease is breast cancer.