Lymphoplasmacytic lymphoma and a CD5+ lymphoproliferative process presenting as composite disease in the bone marrow: a report of two cases

Correct subclassification of B cell lymphoma requires integration of histologic and immunohistochemical findings in addition to results of flow cytometric immunophenotyping, cytogenetic analysis, and molecular studies. Evaluation for the MYD88 L265P mutation and immunohistochemical staining for LEF1 can be helpful in the workup of small B cell lymphomas. In this case report of two diagnostically difficult cases, we present two patients with lymphoplasmacytic lymphoma (LPL) and a CD5+ lymphoproliferative process presenting as composite disease within the bone marrow. In both cases, integration of ancillary studies and results of biopsy at other sites of disease in addition to a careful histologic review and an expanded immunohistochemistry panel were important for the correct final classification.