27. showed increased cyclin D1 staining in 22 CRPC bone metastases compared to 86 primary PC tumors. In our prostatectomy samples, the expression was strongly associated with proliferation but not with Gleason score, pathological status, PSA value, or age at diagnosis. This is in line with previous studies showing that cyclin D1 expression is associated with the proliferation marker Ki-67 but not with other clinicopathological variables 27–31. The gene discussed is MKI67; the disease is pachyonychia congenita.