Acute viral lymphadenitis mimicking low-grade peripheral T-cell lymphoma -A clinicopathological study of nine cases

Acute viral lymphadenitis, especially infectious mononucleosis (IM), often shows the presence of Reed-Sternberg-like cells, resulting in confusion wit h Hodgkin's disease. However, acute viral lymphadenitis requiring different ial diagnosis from non-Hodgkin's lymphoma is not widely recognized. We desc ribe the clinicopathological and immunohistochemical features of lymph node lesions from nine such patients which pose serious problems of differentia l diagnosis from low-grade peripheral T-cell lymphoma. There were three mal es and six females with ages ranging from 21 to 44 years (median 25 years). All patients had "B" symptoms and multicentric lymphadenopathy. The clinic al course was also self-limiting. Each lymph node specimen showed an obviou s expansion of an interfollicular area by pleomorphic and polymorphous infi ltration with an increased number of arborizing postcapillary venules. The infiltrate was composed of variable numbers of small and medium-sized lymph ocytes, immunoblasts, plasma cells in various stage of maturation and occas ional granulocytes. The small lymphocytes usually had regular round nuclei, whereas the medium-sized lymphocytes occasionally showed nuclear pleomorph ism. Hyperreactivity of B-lymphocytes, including hyperplastic germinal cent ers and/or foci of monocytoid B-cells, was seen in parts of the lesion. The majority of the interfollicular T-lymphocytes, including T-immunoblasts, e xpressed CD8 antigen. Various numbers of TIA-1-positive small and medium-si zed T-cells were observed in the paracortical area. Despite these findings, the overall histological picture of this series posed serious difficulties when differentially diagnosing this condition from low-grade peripheral T- cell lymphomas such as angioimmunoblastic T-cell (AILD) and T-zone types, i ndicating that viral lymphadenitis occasionally presents with histological features of AILD and T-zone lymphomas. To avoid overdiagnosis and overtreat ment, we emphasize the need to pay careful attention to the clinical and la boratory findings as well as the morphological features.