This is a composite B-cell lymphoma composed of mantle cell lymphoma and B-cell lymphoma, not further classifiable.

The lambda-restricted B-cell clone is CD5+/CD23-, shows positivity for cyclin-D1 by immunohistochemistry in the bone marrow and FISH study was positive for t(11;14).

The kappa-restricted B-cell clone is the major clone involving the marrow. The differential diagnosis includes marginal zone lymphoma and lymphoplasmacytic lymphoma.

Arguments in favour of lymphoplasmacytic lymohoma include the IgM-restriction and positive MYD88 mutation (tests for this mutation was ordered and came back with a positive result).

Arguments in favour of marginal zone lymphoma include the clinical history (not consistent with Waldenstrom's macroglobulinemia), the morphology (some villous lymphocytes present) in the bone marrow which favours more of a splenic marginal zone lymphoma, and the history of splenomegaly.

While the MYD88 mutation is detected in 80-90% of cases of lymphoplasmacytic lymphoma and IgM MGUS (monoclonal gammopathy of unknown significance) the reference below shows that 7-15% of splenic marginal zone lymphoma (SMZL) do harbour the MYD88 mutation - especially SMZL with igM paraprotein.

To definitively resolve this case, a spleen biopsy may be informative if it is involved by the kappa-restricted B-cell clone (note that the splenomegaly may be due to involvement by mantle cell lymphoma).

This slide shows peripheral blood. See related content for bone marrow biopsy stains.

See related content for references:

1) Martinez-Lopez et al. Am J Surg Pathol 2015, 39:644-651