CD5+ Diffuse Large B-Cell Lymphoma With Leukemic Transformation: A Rare Case With Central Nervous System Involvement, Treated With R-CHOP and Intrathecal Methotrexate/Cytarabine.

Diffuse large B-cell lymphoma (DLBCL) is one of several subtypes of non-Hodgkin's lymphoma, and one that can present in a myriad of ways. One unique and particularly aggressive presentation is leukemic transformation with CD5 positivity, which leads to systemic symptoms, a relatively high peripheral tumor load, and higher rates of CNS involvement. The prevalence of leukemic transformation has not been determined, as published literature is limited to case reports and small case series. CD5 positivity appears to be even rarer and is only found in a small fraction of DLBCL with leukemic transformation. Treatment regimens for this presentation have not been well-established due to the rarity of the disease and paucity of literature on the subject. Our patient, a 76-year-old female with a history of previously treated stage IIIB follicular lymphoma, was found to have CD5+ DLBCL with leukemic transformation. She was treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) along with intrathecal methotrexate (IT MTX)/cytarabine after CNS involvement was diagnosed. The patient tolerated therapy well, with an objective reduction in leukocytosis and blast count. To our knowledge, this is the first such case of CD5+ DLBCL with leukemic transformation treated with dose-reduced R-CHOP and IT MTX/cytarabine. Her response to therapy indicates that this regimen could be a viable option for the treatment of this exceedingly rare disease presentation.