LAUSR

Mantle cell lymphomas (MCLs) are the prototypic B‐cell non‐Hodgkin lymphomas defined by cyclin D1 gene (CCND1; or other cyclin D family gene) rearrangements. However, extremely rare cases of diffuse large B‐cell lymphomas (DLBCLs) harboring CCND1 rearrangements, resulting in cyclin D1 protein expression, have also been reported. In this report, we describe an unusual primary large B‐cell lymphoma of non‐germinal center immunophenotype of the central nervous system (CNS) in an elderly male patient, which was negative for CD5 and SOX11, and exhibited cyclin D1 expression. Fluorescence in situ hybridization analysis detected IGH‐CCND1 and BCL6 rearrangements. This case may represent the first report of a primary CNS DLBCL with IGH‐CCND1 rearrangement. The clinico‐pathologic features that can help differentiate primary CNS MCL from primary DLBCL of the CNS with IGH‐CCND1 rearrangement are discussed.