CDKN2C and plasma cell myeloma: We confirm an important role for bi-allelic inactivation of key genes in myeloma at relapse, including CDKN2C, TP53, RB1, TRAF3 and BIRC3. Homozygous deletion of these genes has previously been identified through the use of mapping arrays.9, 12, 18, 26, 27 and CDKN2C and TP53 are well-accepted poor prognostic markers in myeloma.9, 12, 28, 29 The identification of RB1 as a prognostic marker is more controversial as the association of monosomy of RB1 with poor outcome has fluctuated in recent years.