[Epithelioid cell granuloma in sarcoidosis: light and electron microscopic morphology]

Light and electron microscopic features of epithelioid cell granuloma in sarcoidosis were presented, focusing on the lymph node and the lung which are mostly involved. The distribution of granulomas is frequently conglomerated with occasionally central necrosis. Hamazaki-Wesenberg body in lymph node is considered to be closely associated with Propionibacterium acnes. Granuloma is encircled by reticulin fibers and collagen fibers within the granuloma are detected in electron microscopy. Granuloma may disappear but some develop hyalinization and fibrosis associated with lymphatic and vascular involvement and specific organ structure. Vascular endothelial growth factor is immunohistochemically demonstrated in granuloma, which may be related to microvascular dilatation and proliferation. Thus, epithelioid cell granulomas play an central role in fibrosis and microangiopathy in sarcoidosis.