FTIR imaging has been shown to identify successfully the various cell types present in breast tissue section12,35,43, to reveal breast cancer effect on the extracellular matrix11 and on fibroblasts44,45, to distinguish the different types of lymphocytes (B cells, T cells CD4+ or CD8+)33,46,47 and to identify most breast cancer cell lines grown in vitro after FFPE processing48 or in spheroids13. The gene discussed is CD4; the disease is breast carcinoma.