B2M and neoplasm: Moreover, as loss of both human leukocyte antigen (HLA) class I and II expression is a common phenomenon in aggressive B-cell lymphoma pathogenesis, yet TCR-mediated anti-tumor activity is widely dependent on an intact HLA apparatus, we correlated our observations regarding TCR clonality measures with immunohistochemical expression of HLA class I antigen beta-2-microglobulin (B2M) and HLA class II antigen HLA-DR in all cases in which sufficient FFPE tissue was still available following molecular assessment (18 and 21 respectively).