Angioimmunoblastic T-cell lymphoma with hyperplastic germinal centers: a clinicopathological and immunohistochemical study of 10 cases

An absence of germinal centers is one of the histological characteristics o f angioimmunoblastic T-cell lymphoma (AITL). We report here 10 unusual case s of AITL with hyperplastic germinal centers. The clinical presentation of each patient was characterized by generalized lymphadenopathy, constitution al symptoms and polyclonal hypergammaglobulinemia. The initial biopsy findi ngs of each patient were similar and were characterized by hyperplastic ger minal centers with ill-defined borders and a proliferation of high endothel ial venules (HEV). In the paracortical area there was a mixed infiltrate in cluding irregularly shaped clusters or small nests of clear cells in all ca ses. Moreover, the clear cells invaded the lymphoid follicles, resulting in expansion of the germinal centers, except for one case. Immunohistochemist ry revealed that the tumor cells, including clear cells, were CD4-expressin g T cells. Some of the atypical lymphocytes were also Bcl-6-positive. A maj ority of the follicular dendritic cell networks showed a normal/reactive or an expanded/disrupted pattern in all cases. Moreover, three lesions posses sed a few large irregularly shaped proliferations of follicular dendritic c ells around the HEV Four cases progressed to AITL within a few years. The p resent 10 cases probably represent an early stage of AITL preceding follicu lar dendritic cell hyperplasia. Detection of clear cells, Bcl-6-positive at ypical T lymphocytes, and foci of irregularly shaped proliferation of folli cular dendritic cells appears to be critical for early diagnosis and treatm ent of AITL with hyperplastic follicles.