Spectrum of lymph node pathology in adult onset Still's disease; analysis of 12 patients with one follow up biopsy.

BACKGROUND Adult onset Still's disease (AOSD) is a rare systemic inflammatory disorder of unknown aetiology, frequently accompanying multiple lymphadenopathy. It often mimics malignant lymphoma, and immunohistochemical and molecular studies are needed for definite diagnosis. AIMS To aid in diagnosis and understand the pathogenesis of the disease by clarifying lymph node (LN) pathology in AOSD. METHODS Thirteen biopsies (one follow up biopsy) and medical records of 12 patients were reviewed. Immunohistochemistry, polymerase chain reaction for T cell receptor gamma chain (TCRgamma) and immunoglobulin heavy chain gene rearrangement, and Epstein-Barr virus in situ hybridisation were performed. RESULTS Histologically, LN lesions were classified into four patterns. The most common (six biopsies) showed paracortical hyperplasia, with prominent vascular proliferation, scattered large B/T immunoblasts, and infiltration by reactive lymphocytes and inflammatory cells. In the second pattern (two biopsies), paracortical hyperplasia was accompanied by massive sinus histiocytosis and S-100 positive histiocyte aggregates. The third pattern (three patients) showed an exuberant immunoblastic reaction, in the form of patchy/diffuse infiltration of large T immunoblasts with high mitotic activity, although clonal rearrangement of the TCRgamma gene was not detected. The fourth pattern showed distinct follicular hyperplasia (two cases). One patient with a follow up biopsy showed a pattern change from pronounced follicular hyperplasia to atypical paracortical hyperplasia. CONCLUSIONS AOSD LN lesions show a dynamic histological spectrum, including atypical paracortical hyperplasia, burnt out histiocytic reaction, exuberant immunoblastic reaction, and follicular hyperplasia. During the course of disease, LN reactivity changes and mixed B and T cells are involved in the pathogenesis.