Significant increase of CKS1B amplification from monoclonal gammopathy of undetermined significance to multiple myeloma and plasma cell leukaemia as demonstrated by interphase fluorescence in situ hybridisation.

The genetic events that lead to tumour progression in plasma cell dyscrasia are not well understood. Interphase cytoplasmic fluorescence in situ hybridisation was used to investigate the CKS1B amplification status (at 1q21) in clonal plasma cells from 123 patients: 23 monoclonal gammopathy of undetermined significance (MGUS), 75 multiple myeloma (MM) and 26 plasma cell leukaemia (PCL). While CKS1B amplification was absent in MGUS patients, such amplification (3-8 copies) was detected in 36% of newly diagnosed MM, 52% relapsed MM and 62% PCL (P < 0.001). Our results suggest that CKS1B amplification is associated with transformation from MGUS to MM and progression to PCL.