Diffuse large B-cell lymphoma with both CD5 and cyclin D1 expression-a case report and review of the literature

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin's lymphoma (NHL), representing approximately 25-30% of newly diagnosed adult NHL in Western countries. CD5-positive DLBCL has been reported in 10% of cases in some series. DLBCL with cyclin D1 expression has also been reported in the literature. These cases may sometimes be confused with mantle cell lymphoma (MCL), especially blastoid variant MCL, morphologically and immunophenotypically. Herein, we present an unusual case of a 41-year-old female without significant medical history who presented with a right facial/parotid mass. Morphologically, the tumor showed a diffuse growth pattern of large lymphoid cells with vesicular nuclei, consistent with a DLBCL. Immunostains, however, showed that the tumor cells were positive for both CD5 and cyclin D1. Fluorescence in situ hybridization studies showed a rearrangement of the Bcl-6 gene (3q27) in 29.5% of cells but no evidence of IgH/Bcl-1 [t(11;14)] or IgH/Bcl-2 [t(14;18)] rearrangement. Immunostain for SOX11 was also performed and is negative. The clinicopathologic features of this CD5- and cyclin D1-positive DLBCL are described, and the differential diagnosis between DLBCL and MCL is discussed.