MST1 and rheumatoid arthritis: MST1 promoter hypermethylation had been previously described in not only other cancers such as sarcoma18 and head and neck squamous cell carcinomas,25 but also in non-cancer diseases like autoimmune pancreatitis and rheumatoid arthritis.26 While MST1 inactivation had not previously been evidenced in MPM, our findings are in line with the reports of frequent genetic alterations of Hippo pathway members recently revealed in MPM23 and support the concept that Hippo pathway alterations are key events in pleural carcinogenesis.23,27,28