The frequency of TP53 mutations, which is low at diagnosis (around 3%), increases with relapses and is high in plasma cell leukemia (PCL, >30%) and human myeloma cell lines (HMCLs, >70%), these latter mostly deriving from extramedullary MM and mainly from PCL [4,5,6,7,8]. Here, TP53 is linked to plasma cell leukemia.