Composite chronic lymphocytic leukemia and mantle cell lymphoma involving the bone marrow: a case report and literature review.

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is a clinically indolent lymphoproliferative disorder characterized by accumulation of mature B-cell lymphocytes. Given the common CD5 co-expression, mantle cell lymphoma (MCL) is one of the most important entities in the differential diagnosis. MCL and CLL/SLL might exhibit overlapping morphologic and immunohistochemical features, making diagnosis particularly difficult in cases of composite lymphomas. Here, we present a unique case of composite lymphoma in an 86-year-old male, along with a literature review on the immunophenotypic variability of both MCL and CLL, which should always be confirmed with additional ancillary cytogenetic and molecular studies.