Saturday 31 May 2003
Definition: A granuloma is a solid grouping of inflammatory cells coming together in a lump or solid structure resulting from injury or inflammation or infection. Thus, granulomas are loosely defined as collections of inflammatory cells.
Granulomas may occur anywhere within the liver. Although in some instances they may be more prominent within the portal tracts (e.g., primary biliary cirrhosis), in other disorders they are seen more commonly within the lobules (e.g., drug-induced injury).
However, many liver disorders such as sarcoidosis may demonstrate granulomas within the portal tracts and lobules.
Some granulomas have unusual histologic features very characteristic of one disease entity (e.g., schistosomiasis with pipestem granuloma having a central schistosome ovum).
Special stains may at times be helpful (e.g., AFB or PAS in Mycobacterium avium-intracellulare infection), although in immunocompetent patients, granulomas secondary to an infectious process (especially mycobacteria) are more often negative on special stains.
In addition, some liver diseases may exhibit granulomas that coalesce (e.g., sarcoidosis), forming distinct mass lesions that may be visualized on imaging.
- Epithelioid granulomas are well-demarcated and are composed of variable numbers of lymphocytes, occasional plasma cells, and prominent numbers of activated macrophages which have round to indented clear nuclei and abundant eosinophilic cytoplasm (epithelioid cells).
- Multinucleated giant cells are sometimes seen.
- Inflammatory granulomas are usually smaller than the epithelioid type and are composed of a mixed inflammatory infiltrate consisting of lymphocytes, macrophages, and occasional plasma cells, neutrophils and eosinophils.
- These granulomas may or may not be poorly demarcated. Although occasional multinucleated giant cells can be seen, they are much less frequent than in the epithelioid granulomas.
- A combination of both epithelioid and inflammatory granulomas may be seen within the same biopsy specimen.
hepatic epithelioid granuloma (hepatic tuberculoid granuloma)
hepatic fibrin ring granuloma
mineral oil granuloma
giant cell reparative granuloma
foreign body granuloma (foreign body reaction)
- injection granuloma
- cholesterol granuloma
- tuberculoid granulomatosis
- necrotizing granulomatosis