Transformation of CD5-Negative Follicular Lymphoma into CD5-Positive Diffuse Large B-Cell Lymphoma: A Case Report

Diffuse large B-cell lymphoma (DLBCL) is the most frequent subtype of aggressive lymphomas. Approximately 10% of DLBCL cases express CD5 as a surface antigen. CD5-positive DLBCL can occur as the de novo or secondary type. De novo CD5-positive DLBCL arises without previous lymphoproliferative disease, and secondary CD5-positive DLBCL may or may not manifest as Richter syndrome. The transformation of follicular lymphoma (FL) into DLBCL occurs in approximately one-third of all cases. The transformation of CD5-negative low-grade B-cell lymphoma to CD5-positive DLBCL is extremely rare. We report the clinical features of a rare case that presented with a transformation from CD5-negative FL to CD5-positive DLBL over 11 years. This is the second such case published in the English literature. (Korean J Med 2012;83:263-267)