Composite peripheral T-cell lymphoma not otherwise specified, and B-cell small lymphocytic lymphoma presenting with hemophagocytic lymphohistiocytosis.

We report a case of a 68-year-old female patient who developed hemophagocytic lymphohistiocytosis (HLH) secondary to peripheral T-cell lymphoma (PTCL) not otherwise specified (NOS) that developed in the setting of treatment-resistant B-cell small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL). The patient's B-cell lymphoma had a good initial response to chemotherapy for 4 years, after which it became less responsive and was thought to have undergone transition to a higher-grade lymphoma. Different regimens of chemoradiotherapy were then tried with modest response until the patient presented 3 years later with signs and symptoms of HLH. The patient died 1 month later, and an autopsy was performed. Significant para-aortic lymphadenopathy and splenomegaly were found. Microscopic, immunohistochemical and molecular evaluations confirmed the presence of composite B-cell and T-cell lymphoma in the para-aortic enlarged lymph nodes. Bone marrow examination showed hemophagocytosis, and the liver demonstrated infiltration by activated macrophages with hepatocellular necrosis. This report highlights the importance of searching for a possible underlying T-cell lymphoma in light of HLH. Different theories have been proposed to explain the rare occurrence of concurrent B- and T-cell lymphomas, but the development of HLH in this patient highlights the importance of immune dysregulation as a proposed mechanism to explain some cases of composite lymphomas. A review of the literature and discussion of the relative merits of these hypotheses are presented in the context of this case.