Reaktif Lenfoid Hiperplazi
Özet
Reaktif lenfoid hiperplazi (RLH), lenf düğümlerinin benign ve reaktif büyümesi ile karakterize, sıklıkla enfeksiyonlar başta olmak üzere çeşitli antijenik uyaranlara bağlı gelişen non-neoplastik bir lenfoid proliferasyondur. Klinik olarak lenfadenopati şeklinde ortaya çıkan bu durum, özellikle çocukluk çağında benign nedenlerle ilişkiliyken ileri yaşlarda malignite olasılığı artış göstermektedir. RLH’nin etiyolojisinde viral ve bakteriyel enfeksiyonlar, ilaçlar, çevresel toksinler ve immünolojik uyarılar önemli rol oynamaktadır. Histopatolojik olarak foliküler hiperplazi, diffüz parakortikal hiperplazi ve sinüs hiperplazisi başlıca paternleri oluşturmaktadır. Reaktif foliküler hiperplazide genişlemiş ve polarizasyonunu koruyan germinal merkezler izlenirken, diffüz parakortikal hiperplazi çoğunlukla T hücre aracılı immün yanıtla ilişkilidir. Sinüs hiperplazisi ise belirgin histiyositik proliferasyon ile karakterizedir. İmmünohistokimyasal incelemelerde CD20, CD3, CD21 ve BCL2 gibi belirteçler tanısal açıdan önem taşımaktadır. Özellikle germinal merkezlerde BCL2 negatifliği, RLH’nin foliküler lenfomadan ayrımında kritik bir bulgudur. Bununla birlikte bazı olgularda yalnızca histopatolojik ve immünohistokimyasal incelemeler yeterli olmayabilir; bu durumlarda moleküler yöntemler ve gen yeniden düzenleme analizleri tanıya katkı sağlayabilmektedir.
Reactive lymphoid hyperplasia (RLH) is a non-neoplastic lymphoid proliferation characterized by benign and reactive enlargement of lymph nodes in response to various antigenic stimuli, most commonly infections. Clinically presenting as lymphadenopathy, RLH is generally associated with benign etiologies in childhood, whereas the risk of malignancy increases with advancing age. Viral and bacterial infections, medications, environmental toxins, and immunological stimuli play significant roles in its etiology. Histopathologically, the major patterns include follicular hyperplasia, diffuse paracortical hyperplasia, and sinus hyperplasia. Reactive follicular hyperplasia is characterized by enlarged germinal centers with preserved polarization, while diffuse paracortical hyperplasia is mainly associated with T-cell–mediated immune responses. Sinus hyperplasia is distinguished by prominent histiocytic proliferation. Immunohistochemical markers such as CD20, CD3, CD21, and BCL2 are important for diagnosis. In particular, the absence of BCL2 expression in germinal centers is a critical finding in distinguishing RLH from follicular lymphoma. However, in some cases, histopathological and immunohistochemical findings alone may be insufficient, and molecular techniques together with gene rearrangement analyses may contribute to the definitive diagnosis.
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