We found that FAP expression was negatively correlated with CD8+ T cell infiltration in BRCA, CESC, HNSC, and SKCM, positively correlated with regulatory T cells in LIHC, PCPG, PRAD, and THCA, which suggested that FAP may contribute to the inhibitory immune microenvironment in these cancers. The gene discussed is CD8A; the disease is cancer.