CD20-negative low-grade B cell lymphoma showing immunophenotypic and genotypic features resembling plasma cell myeloma

Here we demonstrate a unique case of CD20-negative low-grade B cell lymphoma showing immunophenotypic and genotypic features resembling multiple myeloma.The female patient had no abnormal masses, splenomegaly, swelled lymph nodes, or bone lesions. Although serum levels of IgG, IgA, and IgM were decreased without M protein, κ-type Bence–Jones protein was observed. In bone marrow, monotonous proliferation of small to medium-sized lymphoid cells was observed without classical myeloma cells, the same histological findings as lymphoplasmacytic lymphoma. The cells were CD38+, CD138+, CD43+, CD44+, CD3−, CD4−, CD5−, CD7−, CD8−, CD10−, CD11b−, CD19−, CD20−, CD21−, CD23−, CD24−, CD25−, CD27−, CD40−, CD45−, and CD56−. Surface or cytoplasmic IgM, κ, or λ were all negative. Chromosomal analysis demonstrated t(11;14)(q13;q32).The present case may belong to a new entity of low-grade B cell lymphoma with the same histological findings as lymphoplasmacytic lymphoma, mainly proliferated in bone marrow whose immunophenotype and genotype are similar to plasma cell myeloma.