Several studies identified tumor-specific hypermethylation of other types of PTPs, such as PTPRO (18,19), PTPRD (20), PTPRG (21,22), PTPN6 (23–25) and PTPN13 (26), reviewed by Jacob and Motiwala (27), and Julien et al (3). This evidence concerns the gene PTPN6 and neoplasm.