The Chromosomal Pattern 14q-Translocation Plus 13q-Deletion Is Characteristic for Multiple Myeloma after a Preceding Monoclonal Gammopathy of Undetermined Significance.

Multiple myeloma (MM) may be preceded by a monoclonal gammopathy of undetermined significance (MGUS), but it is at present unclear whether or not MM post-MGUS is biologically and clinically different from MM de-novo. To address this issue, we have performed a molecular cytogenetic analysis of 32 cases of MM post-MGUS (median time between recognition of MGUS and transition to MM, 7.6 years; range, 2.6 years to 19.5 years) and compared the findings with those of 256 patients with MM de-novo, in whom no previous history of MGUS had been documented. FISH studies of clonal plasma cells (cytoplasmic Ig positive) with probes for IgH translocations [t(14q32)], t(11;14)(q13;q32), t(4;14)(p16;q32), and deletion of 13q14 [del(13q14)] revealed results summarized in Table 1:

Serial studies of MGUS plasma cells and MM post-MGUS plasma cells from 12 of these patients have thus far indicated that all chromosomal abnormalities observed at MM post-MGUS were already present in the MGUS plasma cells; most notably, there was one patient with t(4;14) plus del(13q) who had both abnormalities at the time of MGUS 94 months prior to transition to MM. Collectively, our data suggest that MM post-MGUS is characterized by a distinct chromosomal pattern, in particular a high frequency of t(14q32) plus del(13q14), frequent occurrence of a t(11;14), but low frequency of a t(4;14). We are currently studying the t(14q32) plus del(13q) chromosomal pattern in MGUS to investigate its potential value as a risk factor for transition from MGUS to MM.

Table 1: FISH of MM post-MGUS versus MM de novo