After encountering rare diagnostically challenging cases in which overlap between a low‐level MCL with plasmacytic differentiation and a true PCN with t(11;14), we sought to compare the difference in genomic patterns in PCN and MCL by fluorescence in situ hybridization (FISH) using the CCND1/IGH probe set with the goal to evaluate possible differentiating characteristics potentially to aid in diagnostically challenging cases. This evidence concerns the gene CCND1 and mantle cell lymphoma.