Epstein-Barr virus-related atypical lymphoproliferative disorders in Waldeyer's ring: a clinicopathological study of 9 cases.

BACKGROUND AND STUDY AIM: Because of the small biopsy specimens in the Waldeyer's ring (WR) the differential diagnosis between Epstein-Barr virus (EBV)-associated lymphoproliferative disorder (LPD) and malignant lymphoma is occasionally difficult. We report here clinicopathological, immunohistochemical and genotypic findings of 9 cases of EBV-associated LPDs in WR. PATIENTS AND METHODS: Using formalin-fixed paraffin-embedded sections, histological analyses, immunohistochemistry, in situ hybridization and polymerase chain reaction were performed.
RESULTS: Clinically, all 9 cases showed more than one atypical clinical finding of infectious mononucleosis including absence of systemic symptoms, absence of atypical lymphocytosis and age over 30 years. Histologically, 3 types were delineated: (1) Hodgkin lymphoma-like (n = 1), (2) T cell/histiocyte-rich large B cell lymphoma-like (n = 4), and (3) marginal zone B cell lymphoma of mucosa-associated lymphoid tissue (MALT)-like (n = 4). The in situ hybridization study demonstrated EBV-encoded small RNA (EBER)+ cells in all 9 lesions. The immunohistochemical and flow cytometry study demonstrated the reactive nature of the B cells in all 9 lesions. However, 3 of our 7 cases examined demonstrated immunoglobulin heavy chain gene rearrangement on PCR study. There was no development of B cell lymphoma in any of the 3 lesions demonstrating IgH rearrangement.
CONCLUSION: EBV-associated LPDs of the WR showed marked histological diversity. Among these, a MALT-like pattern was frequently seen. Marginal zone B cell lymphoma frequently affects WR. We emphasized that EBV-associated LPD should be added to the differential diagnosis of primary tonsillar MALT-type lymphoma.