Leukemic Presentation of CD5-Positive Diffuse Large B-Cell Lymphoma: A Case Report and Literature Review.

CD5-positive diffuse large B-cell lymphoma (CD5+ DLBCL) is a rare and highly aggressive subtype of DLBCL, commonly characterized by extranodal involvement, an activated B-cell/non-germinal center B-cell phenotype, and a poor prognosis. Although CD5+ DLBCL frequently presents at an advanced stage, leukemic presentation-defined by the presence of abundant circulating malignant B-cells in the peripheral blood-is exceedingly rare, with only a limited number of cases reported globally. We herein report, to the best of our knowledge, the first reported case in Korea of relapsed CD5+ DLBCL with leukemic presentation. The patient exhibited a high tumor burden, a double-expressor phenotype, and rapid disease progression despite multiple lines of therapy. This case report highlights the diagnostic and therapeutic challenges in managing CD5+ DLBCL with leukemic presentation and emphasizes the need for further studies.