[Transformation of CD5-positive nodal marginal zone lymphoma to diffuse large B-cell lymphoma]

Nodal marginal zone lymphoma (NMZL) is a form of nodal B-cell lymphoma exhibiting proliferation of abnormal lymphocytes at the circumference of the mantle zone in the lymph nodes. Although the outcome of patients with this disease is often favorable, we recently encountered a patient with a CD5-positive NMZL who was resistant to chemotherapy. A 67-year-old woman complaining of systemic lymph node swelling was referred to our hospital. After biopsy of the neck lymph node, she was diagnosed with CD5-positive NMZL. Disease progression was revealed after 16 months, and she was initially treated with chemotherapy consisting of rituximab, cyclophosphamide, vincristine, and prednisolone (R-CVP). However, this therapy was ineffective. Subsequent therapy with rituximab and bendamustine also failed to induce remission. A rebiopsy revealed that the NMZL had transformed into a diffuse large B-cell lymphoma. This patient died after 2 years from the initial diagnosis due to lymphoma progression. Cases of CD5-positive NMZL are rare; thus, it is difficult to study the clinical implications of CD5 expression in this disease. Here we describe the current understanding of CD5 expression in NMZL.