Infectious mononucleosis mimicking lymphoma: distinguishing morphological and immunophenotypic features

• Published in: Modern pathology 2012-08, Vol.25 (8), p.1149-1159
• Main Authors: Louissaint, Abner, Ferry, Judith A, Soupir, Chad P, Hasserjian, Robert P, Harris, Nancy L, Zukerberg, Lawrence R
• Format: Article
• Language: English
• Subjects: 692/699/249/1623; 692/699/67/1990/291; 692/700/139/422; Adult; Age; Aged; Antigens, CD - metabolism; Asymptomatic; Bcl-2 protein; Bcl-6 protein; Biomarkers - metabolism; Biopsy; Child; Diagnosis, Differential; Epstein-Barr virus; Female; Herpesvirus 4, Human - isolation & purification; Humans; Immunoglobulin Light Chains - metabolism; Immunoglobulins; Immunohistochemistry; Infection; Infections; Infectious mononucleosis; Infectious Mononucleosis - diagnosis; Infectious Mononucleosis - metabolism; Infectious Mononucleosis - virology; Interferon regulatory factor 4; Laboratories; Laboratory Medicine; Light chains; Lymph nodes; Lymph Nodes - pathology; Lymph Nodes - virology; Lymphatic system; Lymphocyte Activation; Lymphocytes - pathology; Lymphocytes B; Lymphoid tissue; Lymphoma; Lymphoma - diagnosis; Lymphoma - metabolism; Male; Medicine; Medicine & Public Health; Middle Aged; Mimicry; Mononucleosis; Morphology; Mucosa; Necrosis; original-article; Pathology; Proto-Oncogene Proteins c-bcl-6 - metabolism; Reed-Sternberg Cells; Tonsil; Tonsillitis; Young Adult
• ISSN: 0893-3952; 1530-0285
• DOI: 10.1038/modpathol.2012.70

The diagnosis of infectious mononucleosis (acute Epstein–Barr virus (EBV) infection) is usually made on the basis of clinical and laboratory findings. However, an atypical clinical presentation occasionally results in a lymph node or tonsillar biopsy. The morphological features of EBV-infected lymphoid tissue can easily mimic lymphoma. Furthermore, the immunophenotype of the immunoblasts has not been well characterized. To assess the morphological spectrum of acute EBV infection and the utility of immunohistochemistry in diagnosing difficult cases that resemble lymphoma, we reviewed 18 cases of acute EBV infection submitted in consultation to our institution with an initial diagnosis of/or suspicion for lymphoma. Patients included nine male and nine female individuals with a median age of 18 years (range 9–69). Biopsies were obtained from lymph nodes (3/18) or Waldeyer's ring (15/18). Infectious mononucleosis was confirmed by monospot or serological assays in 72% of cases (13/18). All cases featured architectural distortion by a polymorphous infiltrate with an immunoblastic proliferation, sometimes forming sheets. Reed–Sternberg-like cells were present in 8/18 (44%) of the cases. Infiltrates were often accompanied by necrosis (10/18) and mucosal ulceration (6/15). The majority of immunoblasts in all cases were CD20+ B cells with a post-germinal center immunophenotype (strongly positive for MUM1/IRF4 (18/18), CD10− (18/18 negative) and BCL-6− (16/18 negative; 2/18 faint BCL-6 expression in