OBJECTIVETo investigate the clinicopathologic characteristics of adult patients with atypical infectious mononucleosis(IM).

METHODSFrom January 2003 to December 2013, a total of 5 cases of atypical IM misdiagnosed as lymphoma were selected, and the clinico-pathological characteristics and efficacy of treatment were analyzed. Biopsy of lymph node or tonsil was performed to evaluate the possibility of lymphoma. Peripheral blood EBV antibody and EBV-DNA were examined by ELISA and real-time fluorescence quantitative PCR, respectively.

RESULTSAll the cases were considered as lymphoma on the basis of morphological features in initial evaluation before relapse. These features included a florid immunoblastic proliferation, distortion of the underlying nodal or tonsillar architecture and the presence of necrosis. The immunophenotypic features, EBV encoded RNA (EBER) in situ hybridization and the gene rearrangement of immunoglobulin or T cell receptor may be helpful for the distinction of atypical IM from lymphoma.

CONCLUSIONIM as EBV-related lymphoproliferative process shows marked clinical and histological diversity. Atypical case of IM may mimic many different type of lymphoma in clinical and pathologic features, and the misdiagnosis should be avoided by using molecular and pathological examination.