Form and function of sarcoid granulomas

Abstract

The pathological feature of sarcoidosis is the presence of granulomas in more than one system. What is a granuloma? Morphologically a granuloma consists of a focal collection of mononuclear, epithelioid cells, sometimes giant cells, odmixed and surrounding lymphocytes, plasma cells and fibro-blasts. Inclusion bodies, Schaumann and asteroid, may be present. Necrosis may be present or absent. All are features of chronic inflammation, and unfortunately are not diagnositc of any one causative agent. The cell characteristic of granulomatous inflammation is the bone marrow derived epithelioid cell. Epithelioid cells are metabolically active and in some diseases, such is tuberculosis, behave as phagocytic macrophages. What is the function of epithelioid cells in sarcoidosis? It is potentially phagocytic but has never been shown to contain any indentifiable infective agents. It has all the potentials of a synthesising cell whose products may well influence persistence of the granulomas. A detailed study of the nature and function of epithelioid cells in sarcoidosis will be presented based on light and electron microscopy, histochemistry and tests of lymphocyte function.