PRF1 and basal cell carcinoma: The most relevant feature of these TRM cells, identified as CD8+ CD103+ T cells, common to breast, lung, and basal cell cancers, was an elevated expression of genes coding for immune checkpoint receptors, such as PDCD1 (PD-1), CTLA4, HAVCR2 (TIM-3), TIGIT, and LAG3, and a higher expression of GZMB (granzyme B) and PRF1 (perforin) compared with CD8+ CD103– T cells [155, 156, 161, 163].