A 3-way collision tumor of the upper respiratory tract: a composite of 2 immunophenotypically distinct mantle cell lymphomas and a plasmacytoma

Composite lymphoma (CL) is composed of 2 or more morphologically and immunophenotypically distinct lymphomas in a single anatomical site. Here we report a unique CL of the upper respiratory tract in an elderly male patient. Morphologically, the lymphoma was composed of 2 distinct and well-demarcated areas consisting of monotonous small to medium-sized lymphocytes and sheets of mature-appearing plasma cells. Immunophenotyping by both flow cytometry and immunohistochemistry revealed that the small to medium-sized lymphocytes were composed of 2 distinct subpopulations sharing a CD5⁺/CD19⁺/CD20⁺/CD22⁺/CD23^-/FMC-7(+)/cyclin D1(+) immunophenotype but with different immunoglobulin (Ig) light and heavy chain expression, consistent with 2 immunophenotypically distinct mantle cell lymphomas (MCLs); the plasma cells were composed of CD38(bright +)/CD138⁺/IgG κ-restricted plasma cells, consistent with a plasmacytoma. Fluorescence in situ hybridization showed the t(11;14) translocation present in the lymphocyte region but absent in the plasma cell area. Ig heavy chain gene rearrangement studies on manually dissected populations showed 2 distinct patterns for the MCL and plasmacytoma. To our knowledge, this is the first report of a 3-way CL consisting of 2 immunophenotypically distinct MCLs and a plasmacytoma.