Given supportive evidence from the literature of the contributions of aberrant methylation and expression of MTHFR and DNMTs, such as DNMT1, DNMT3A, and DNMT3B, in other types of cancer, such as those of the breast, lung, and brain [15,16,17], we performed the present study to evaluate the methylation levels of these genes in thymomas of patients with MG. The gene discussed is DNMT3A; the disease is cancer.