Germinal Merkezlerin Progresif Transformasyonu
Özet
Germinal merkezlerin progresif transformasyonu (GMPT), lenf nodlarında germinal merkezlerin belirgin genişlemesi ve mantle zon küçük B lenfositlerinin germinal merkez içine kolonizasyonu ile karakterize benign reaktif bir histopatolojik paternidir. Bu süreç sonucunda germinal merkez–mantle zon sınırı silikleşir ve folliküller düzensiz mozaik bir yapı kazanır. GMPT çoğunlukla persistan lenfadenopati nedeniyle yapılan eksizyonel biyopsilerde saptanır ve özellikle nodüler lenfosit predominant Hodgkin lenfoma (NLPHL) ile ayırıcı tanıda önem taşır. En sık servikal lenf nodlarında görülür ve genellikle ağrısız, yavaş büyüyen lenfadenopati ile prezente olur. Histopatolojik olarak büyümüş düzensiz germinal merkezler, mantle zon hücre kolonizasyonu ve korunmuş ancak genişlemiş folliküler dendritik hücre ağı dikkat çekicidir. İmmünohistokimyasal incelemelerde CD20 ve IgD mantle zon kolonizasyonunu gösterirken, CD10 ve BCL6 reaktif germinal merkez fenotipini destekler. Germinal merkezlerde BCL2 negatifliği, folliküler lenfomadan ayrımda önemli bir bulgudur. GMPT ayrıca IgG4-ilişkili hastalık spektrumu içinde GMPT-benzeri reorganizasyon paternleriyle de ilişkilendirilmektedir. Klinik seyir genellikle benign olup tedavi gerektirmez; ancak NLPHL ile birliktelik olasılığı nedeniyle uzun dönem klinik izlem önerilmektedir.
Progressive transformation of germinal centers (PTGC) is a benign reactive histopathological pattern characterized by marked enlargement of germinal centers and infiltration of mantle zone small B lymphocytes into the germinal center. This process results in blurring of the germinal center–mantle zone interface and development of an irregular mosaic follicular architecture. PTGC is most commonly identified in excisional lymph node biopsies performed for persistent lymphadenopathy and is of particular importance in the differential diagnosis with nodular lymphocyte predominant Hodgkin lymphoma (NLPHL). It most frequently involves cervical lymph nodes and typically presents as painless, slowly enlarging lymphadenopathy. Histopathologically, enlarged irregular germinal centers, mantle zone B-cell colonization, and a preserved but expanded follicular dendritic cell network are characteristic findings. Immunohistochemically, CD20 and IgD highlight mantle zone colonization, whereas CD10 and BCL6 support preservation of the reactive germinal center phenotype. Lack of BCL2 expression within germinal center B cells is an important feature distinguishing PTGC from follicular lymphoma. PTGC-like follicular reorganization patterns have also been described in the spectrum of IgG4-related disease. The clinical course is generally benign and indolent, usually requiring no specific treatment; however, long-term clinical follow-up is recommended because of the occasional association with NLPHL.
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