CTLs (ie, CD8+ cells) are tumor-suppressive and play a critical role in the effectiveness of ICB in cancer.19 In MPM, CTLs typically represent approximately 5%–15% of the total immune infiltrate,20 21 while CTL deserts are rare.22 One study reported more CD8+ cells in PD-L1+ tumors than PD-L1− ones,23 implying that this routinely used biomarker may also predict CTL infiltration. This evidence concerns the gene CD8A and cancer.