Schaumann body

**Definition:** Schaumann bodies (conchoidal bodies) are round to oval, basophilic, laminated (concentrically layered) inclusions composed of calcium carbonate and calcium phosphate complexed with proteins. They sit within the cytoplasm of multinucleated giant cells or macrophages in granulomas.

**Pathophysiology:** In sarcoidosis, CD4+ Th1 cells respond to an unknown antigen and release IFN-gamma and TNF-alpha. This activates macrophages, which form non-caseating granulomas and fuse into giant cells. Schaumann bodies are thought to be lysosomal residual bodies. They form by calcium and protein deposition in degenerating or overactive macrophages and giant cells. Activated macrophages also express 1-alpha-hydroxylase, which converts 25-OH vitamin D to 1,25-(OH)2 vitamin D. This causes hypercalcemia and hypercalciuria, a related calcium-handling abnormality.

**Histology (high-yield trio of giant cell inclusions):** - **Schaumann bodies:** laminated calcifications, basophilic, concentric rings - **Asteroid bodies:** star-shaped eosinophilic inclusions with radiating spikes, composed of cytoskeletal proteins (vimentin) in the giant cell - **Hamazaki-Wesenberg bodies:** yellow-brown, spindle or ovoid lysosomal structures in lymph node sinuses, which can mimic fungi

**Clinical significance (sarcoidosis):** - Classically a young adult African American woman, or a person of Scandinavian descent - Bilateral hilar lymphadenopathy, with interstitial lung disease causing restrictive physiology - Erythema nodosum, lupus pernio, uveitis, and Löfgren syndrome (erythema nodosum, hilar adenopathy, arthralgia) - Elevated ACE, hypercalcemia, and elevated CD4:CD8 ratio in BAL fluid - Non-caseating granulomas on biopsy, with inclusions such as Schaumann and asteroid bodies - Treatment: corticosteroids

**Key exam points:** - Schaumann bodies are **not pathognomonic**. They also appear in berylliosis, tuberculosis, leprosy, Crohn disease, and other granulomatous conditions. - Granulomas in sarcoidosis are non-caseating, which distinguishes them from the caseating granulomas of TB. - Do not confuse them with Psammoma bodies (concentric calcifications seen in papillary thyroid carcinoma, meningioma, serous ovarian cystadenocarcinoma, and mesothelioma). Both are laminated calcifications, but psammoma bodies are tumor-associated and form extracellularly, while Schaumann bodies are intracellular within giant cells. - Do not confuse them with Michaelis-Gutmann bodies (malakoplakia), which are also calcified, laminated intracellular inclusions, but are found within macrophages (von Hansemann cells) in the bladder and are linked to E. coli infection.