Granuloma

An organized cluster of immune cells (primarily macrophages) that forms when the body attempts to isolate and wall off substances it cannot easily eliminate. Possible causes for the chronic inflammatory reaction are infections (tuberculosis, histoplasmosis, blastomycosis, schistosomiasis, cat scratch disease, syphilis, leprosy), foreign bodies (splinters, surgical sutures, tattoo ink, cosmetic fillers), autoimmune disease (sarcoidosis, Crohn's disease, granulomatosis with polyangiitis), or genetic disorders (chronic granulomatous disease).