HOXD9 and thymoma: Bisulfite pyrosequencing in 46 TEN and 20 paired thymus tissues revealed higher promoter methylation of G protein subunit gamma 4 (GNG4), growth hormone secretagogue receptor (GHSR), homeobox D9 (HOXD9) and spalt like transcription factor 3 (SALL3) in TC than in thymoma.