Granuloma

A granuloma - plural granulomas or granulomata - is a discrete region of granulomatous inflammation defined by its histology after biopsy:

• epitheloid cells at its centre
• fusion of epitheloid cells to form a foreign body giant cell - the key feature

There may also be:

• lymphocyte mantle surrounding epitheloid cells
• evidence of aetiological agent e.g. tuberculosis bacillus
• fibroblast proliferation with or without fibrin deposition
• plasma cells
• less frequently, neutrophils

A tuberculous granuloma is termed a tubercle. Rheumatoid nodules of rheumatoid arthritis contain granulomas.

The causes of granulomas are detailed under granulomatous inflammation in the submenu.