Non-paraskeletal extramedullary disease is associated with high rates of high risk cytogenetic alterations and has a distinct transcriptional profile

selected to identify those above the median age and diminish overlap between groups.Results: African American (AA) were enriched in the ≤ 45 year groups in both cohorts (WCM 31% vs 13%, MMRF vs 15%, p 45 years at diagnosis (183 patients) as a control in the WCM cohort showed similar results.Lower incidence of deletion 13q and gain 1q in the ≤ 45 years cohort (35% vs 50% p = 0.03, and 22% vs 42% p < 0.01) when compared to the ≥ 63 year cohort was seen.There were no differences in the rate of recurrent translocation, deletion, or mutations in MM.Enrichment of the CD-1 (associated with Cyclin D1) subgroup in the ≤ 45 years subgroup, while the LB (low bone) and HP (associated with hyperdiploidy) were enriched in the older group.Mutational signature analysis was done including all single nucleotide variants, the ≥ 63 year had higher mutational burden (3.8 vs 3.3 mut/Mb, p < 0.01), due to higher count and frequency of clock-like signatures (COSMIC 1 and 5), while there were no differences in other signatures.Conclusions: Young MM represents a distinct clinical enriched for AA, lower ISS stage and likely higher functional class and physiologic reserve (higher ASCT and lower ECOG), leading to improved PFS/OS, likely derived from better tolerance to highly active therapies and less attrition after progression.We identified a distinct molecular subgroup enriched for CD-1 signature and lower rates of deletion 13q and gain 1q, with a higher mutational burden due to higher clock-like signatures which suggest a later time of disease onset.There were no differences in the rate of recurrent translocation, hyperdiploidy or mutations.Genomic studies focused in AAs/Hispanics germline and somatic factors associated with MM are required to identify the biological origin for the observed differences.