Remarkably, in the present study, HTR1F expression exhibited a significantly negative correlation with tumor mutation burden (TMB) expression in four tumors (CESC, LAML, HNSC, and LUSC) and a positive correlation with the microsatellite instability (MSI) in COADREAD, BRCA, STES, KIPAN, STAD, UCEC, and HNSC. The gene discussed is HTR1F; the disease is neoplasm.