KMT2A-MAML2 gene fusion was reported in 4% thymomas (10 of 242), and was considered specific to type B2 and B3 thymomas.[18] Here, we showed the mutation of KMT2A can occur in thymic adenocarcinoma and type A thymoma, suggesting that KMT2A mutation may not specific to type B2 and B3 thymomas, but a common genetic change in thymic tumorigenesis. This evidence concerns the gene KMT2A and thymus gland adenocarcinoma.