Leukemic mantle cell lymphoma and chronic lymphocytic leukemia: a rare composite lymphoma and literature review

Composite lymphomas are rare entities that either represent a collision of two separate lymphomas, or one lymphoma that expresses two distinct phenotypes. Mantle cell lymphoma has been reported in some composite lymphomas, but when combined with chronic lymphocytic leukemia, it can be difficult to recognize because of the phenotypic overlap of these two entities. We report a case of a 75-year-old male with a slowly progressing lymphocytosis, but who was otherwise asymptomatic. Flow cytometry revealed two different populations, one showing bright Lambda positivity and CD5(+), while the other was positive for both lambda and kappa and was CD5(+). Subsequently, cytogenetics revealed two different populations, one with a trisomy 12 and the other with a t(11;14). Additionally, immunohistochemistry on a bone marrow biopsy showed SOX-11 to be negative and cyclin D1 to be positive on scattered lymphocytes. This was consistent with a composite lymphoma of leukemic mantle cell lymphoma and chronic lymphocytic lymphoma.