Non-necrotizing granulomas are the key histopathologic feature of sarcoidosis. These are well-formed, epithelioid granulomas found in lymph nodes and in a lymphatic distribution in the lung. Rare microscopic foci of necrosis are not incompatible with the diagnosis, but, as in all cases, special stains for AFB and fungi should be done to rule out infection. Various inclusions can be seen in the granulomas. These include the deeply basophilic, lamellar Schaumann bodies, calcium salt crystals, asteroid bodies and Hamazaki-Wesenberg bodies.
Sarcoidosis is a diagnosis of exclusion for the pathologist.
The differential diagnosis includes infections and berylliosis. Special stains and history are needed to exclude these. Occasionally, hypersensitivity pneumonitis may display numerous granulomata, but these are usually poorly-formed and accompanied by an interstitial pneumonitis. The clinical course is benign in most cases. Current Concepts of the Pathogenesis of Sarcoidosis.