Granulom

Granulom, commonly written as granuloma in English, denotes a localized nodular lesion formed by chronic granulomatous inflammation. It is typically composed of concentrated macrophages that have transformed into epithelioid cells, often accompanied by multinucleated giant cells, and surrounded by lymphocytes; over time, fibroblasts and connective tissue may encase the lesion.

Granulomas form when the immune system attempts to wall off persistent irritants, such as certain microbes, inert foreign material, or autoimmune stimuli. The histologic pattern reflects the nature of the stimulus: caseating (necrotic) granulomas are classically associated with Mycobacterium tuberculosis and some fungi, whereas noncaseating granulomas are more typical of sarcoidosis and Crohn’s disease, though exceptions occur.

Common etiologies include infectious agents (tuberculosis, atypical mycobacteria, Histoplasma and other fungi), foreign bodies (silica, talc, splinters), and immune-mediated diseases (sarcoidosis, Crohn’s disease, granulomatosis with polyangiitis). Granulomas may form in many organs, most often the lungs and regional lymph nodes, but can also involve the liver, skin, eyes, and bones.

Clinically, granulomas may be asymptomatic or cause symptoms related to their location or underlying disease. Imaging can reveal nodules, masses, or organ enlargement; diagnosis relies on tissue biopsy showing the characteristic granulomatous inflammation and, when appropriate, identification of the causative agent.

Management targets the underlying cause. Infections require appropriate antimicrobial therapy; inflammatory granulomas are treated with immunomodulatory agents such as corticosteroids or other therapies tailored to the disease. Some granulomas resolve, while others may persist and lead to fibrosis.