Another prospective case series reported MSI-H/dMMR in 3.1% of PC patients, while an unselected cohort study of 3,607 patients with personal history of PC reported the presence of mutations germline in MLH1, MSH2, MSH6 or PMS2 in 1.7% of cases (19, 20). Here, MLH1 is linked to pachyonychia congenita.