Abstract
Mantle cell lymphoma (MCL) is a mature B-cell lymphoma associated with cyclin D family rearrangements and typically expresses CD5 and cyclin D1. Epstein-Barr virus- (EBV-) positive MCL is rare, and the role of EBV infection and its transformation in MCL remains unclear. We present a case of CD5-negative classic MCL that progressed to an EBV + pleomorphic MCL six years after the initial diagnosis. Molecular studies confirmed the same clonal origin. To the best of our knowledge, the EBV-positive transformation of CD5-negative MCL into a pleomorphic variant has rarely been reported, and its recognition is important for the diagnosis and the management of patients with MCL.