Granuloma (plural
granulomas or
granulomata) is an
inflammation found in many diseases. It is a collection of
immune cells known as
histiocytes. Granulomas form when the
immune system attempts to wall off substances it perceives as foreign but is unable to eliminate. Such substances include
infectious organisms including
bacteria and
fungi, as well as other materials such as
keratin and
suture fragments. The adjective
granulomatous means
characterized by granulomas.