B2M and neoplasm: In the last decade, several pathological biomarkers including PD-L1 tumor proportion score (TPS), tumor mutational burden (TMB), human leucocyte antigen (HLA) class I and II expression, β2-microglobulin (β2m) mutations, tumor microenvironment (TME) composition, and gene expression profiles (GEPs) have been investigated with various results (12–16).