Homologous recombination deficiency (HRD) leads to the accumulation of a large amount of DNA with damage that cannot be repaired, thus increasing genomic instability, which may be one of the reasons for the higher TMB level of LUADs with co-mutation of FAT3 and LRP1B. This evidence concerns the gene FAT3 and hypoparathyroidism-retardation-dysmorphism syndrome.