Granuloma

A gathering of activated macrophages that are grouped together into a nodule, and surrounded by lymphocytes. The macrophages often develop an epithelial-like character, thus aquiring the name epitheloid cells.

Epitheloid Granuloma
A sharply circumscribed nodule that mainly consists of epitheloid cells(modified macrophages).
 * Tuberculous granuloma.
 * Sarcoidal granuloma.

Histiocytic Granuloma
An ill-defined nodule that consists of phagocytic histiocytes(tissue macrophages).
 * Foreign-body granuloma.
 * Rheumatoid granuloma.
 * Rheumatic granuloma.

Sarcoid Granuloma
Small granulomas that mostly consists of epitheloid cells. No necrotizing center, but fibrosis may be present. The outer layer consists mostly of collagen. Sarcoid granulomas can occure in:
 * Sarcoidosis.
 * Crohn`s disease.
 * Berylliosis.
 * Extrinsic Allergic Alveolitis.
 * Primary Billiary Cirrhosis.

Tuberculous Granuloma
A large circumscribed granuloma consisting of epitheloid cells around a caseous necrotic core with interspersed Langhans cells. The outer layer consists mostly of lymphocytes. Tuberculous granulomas can occure in:
 * Tuberculosis.
 * Leprosy.
 * Syphilis - A granuloma in syphilis is called gumma. They have coagulative necrosis and central vessels in their core, and plasma cells in their peripheral zone.

Pseudotuberculous Granuloma
As the name implies, they are quite similar to tuberculous granulomas. They are ill-defined granulomas consisting of macrophages and epitheloid cells. Granulocytes(mostly neutrophils) are present in the caseous core. They may form abscesses. Pseudotuberculous granulomas can occure in:
 * Yersinia Pseudotuberculosis.
 * Brucellosis.
 * Listeriosis.
 * Histoplasmosis.
 * Cryptococcosis.
 * Typhoid fever.

Rheumatic Granuloma
A granuloma with specialized macrophages(called Anitchov cells)around a core of fibrinoid collagen necrosis. Aschoff cells(a variant of giant cells) are interspersed between the other cells, while lymphocytes make up the outer layer. Rheumatic granulomas mostly occure in myocardium and only in rheumatic fever.

Rheumatoid Granuloma
A granuloma with a core of fibrinoid collagen necrosis, surrounde by a wall of epitheloid cells. Several centimeters in diameter. Lymphocytes are present in the outer layer. Often occuring in multiple subcutaneous locations and articular nocules in rheumatoid arthritis.

Foreign-Body Granuloma
A granuloma with epitheloid cells surrounding a material that cannot be broken down, or that provides large enough difficulties in doing so. The foreign body is surrounded by epitheloid cells and giant cells. The outer layer consists of lymphocytes, fibroblasts and vessels.

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