GSTP1 and renal cell adenocarcinoma: So far, 10 DNA methylation-based studies (e.g., using VHL, RASSF1A, P16, P14, RARB, TIMP3, GSTP1, APC) for RCC detection have been published [58,59,60,61,62,63,64,65,66,67] and only 33.33% of these had an RCC cohort with more than 50 patients [60,63,64].