**9. Tumor mutational burden (TMB) as TNBC biomarker**

TMB is defined as the measurement of non-synonymous mutations present in tumor cells. Here mutations lead to enhanced expression of neoantigens in terms of MHC I class antigens thereby increasing the visibility of cancer cells to T cells. However, limited data for TMB is reported while the frequencies of TMBs are found to be significantly higher in TNBC comparative to the other breast cancer sub types [57]. Therefore, the presence of TMB is linked with immunogenicity in several tumor types [58]. A recent study revealed no significant difference for breast cancer patients pretreated with ICIs (immune checkpoint inhibitors) in survival. Therefore, it is assumed that TMBs alone are not supposed to represent a sole predictor as biomarker evoking the need to enrich the available information regarding TNBC biomarkers [58, 59].
