Multiple Myeloma with IGH-Involving del(14q): Report of 34 Cases.

Chromosomal translocations involving the IGH locus on 14q32 are a hallmark of B-cell malignancies. These translocations are particularly frequent in non-hyperdiploid (NHD) multiple myeloma (MM), representing approximately 50% of myeloma cases. MM-associated primary t(14q32) target at least 7 partner genes including cyclins D (CCND1, −D3), MAF transcription factors (CMAF, MAF B and A) and MMSET/FGFR3. Some of the translocations are predictive of clinical outcome. Recently, we identified a novel interstitial del(14q) involving IGH and recurrent in chronic lymphocytic leukaemia and MM (Pospisilova et al, Leukemia, 2007). In spite of extensive studies, the mechanism(s) and molecular consequences of del(14q) remain unknown. We report here 34 cases of plasma cell (PC) malignancies with del(14q) involving IGH, as proven by FISH. Cases were collected in UK and Belgium. The estimated incidence of these aberrations in PC malignancies was 1.4%. There were 13 female and 21 male patients ranging in age from 49 to 86 years (average 68). Twenty seven patients had MM, one had SMM and 6 had MGUS. In almost all cases, the del(14q) was detected at diagnosis. Clinical data of the reported cases have been collected. The del(14q) were roughly mapped by FISH and grouped into 3 categories according to the proximal breakpoint:

1. del(14)(q24.1q32.33) involving the ZFP36L1 region (11 cases);

2. deletions proximal to ZFP36L1 (14 cases) and

3. deletions distal to ZFP36L1 (7 cases).

The size of del(14q) was not determined in 2 cases. Biallelic deletion of TRAF3/14q32.33 recurrently occurring in MM, was detected by FISH in 1 out of 9 analyzed cases. Additional FISH analysis showed that the del(14q) was predominantly associated with NHD tumors (62% vs 38% with hyperdiploid karyotypes) and frequently (60%) accompanied by del(13q), regarded as a poor prognostic factor. All reported cases were negative for t(4;14) and t(11;14); they also showed a normal status of CCND3, CMAF, MAFB and CMYC, when examined. A gain of 1q/CKS1B was found in 57% (8/14) of analyzed cases. The expression pattern of cyclin D1−D3 has been examined.