Dalland JC, Smadbeck JB, Sharma N, et al. - Given plasma cell neoplasms (PCN) and mantle cell lymphoma (MCL) can both harbor t(11;14)(q13;q32) (CCND1/IGH), but it can be morphologically difficult in some cases, especially at low levels of disease, to differentiate between these entities in the bone marrow, thus, researchers herein compared the difference in CCND1/IGH via fluorescence in situ hybridization (FISH) in PCN and MCL to assess for possible distinguishing features. This analysis involved 326 cases of MCL with t(11;14) and 279 cases of PCN with t(11;14). An “atypical” pattern was defined as any deviation from the “typical” pattern (which was defined as 3 total CCND1 signals, 3 total IGH signals, and 2 total fusion signals). An “atypical” pattern was further stratified into “gain of fusion” vs “complex” patterns. In PCN vs MCL, an atypical FISH pattern was exhibited by a significantly higher proportion of cases. Presence of a complex CCND1/IGH FISH pattern was more often detected in PCN vs MCL, indicating likely differences in the genomic mechanisms underlying these rearrangements in plasma cells vs B cells.