B2M and cancer: We assessed gene wide and site-specific selection pressures in the context of trends across categories of cancer associated genes, i.e., oncogenes (GRB2, FGL2 and CDC42), tumour suppressor genes (LITAF, Casp8 and BRCA2) and immune genes (IL2, CD274 and B2M), and extended the analyses to mammalian taxa on the order, super order and infraclass level.