Fortunately, in addition to an immunoprofile characteristic of plasma cell myeloma (diffuse positivity for CD138, negativity of CD19 and dim to negative expression for CD45), both cases demonstrated cyclin D1 expression, which, while characteristic of mantle cell lymphoma and hairy cell leukemia, is not a feature of B-cell lymphoma that commonly shows plasmacytic differentiation, such as lymphoplasmacytic lymphoma [10]. This evidence concerns the gene CCND1 and hairy cell leukemia.