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Created page with " * Granulomatous inflammation is usually caused by organisms of low virulence but great persistence, or by implanted foreign bodies. * Classically appears as a '''granuloma''..."
* Granulomatous inflammation is usually caused by organisms of low virulence but great persistence, or by implanted foreign bodies.
* Classically appears as a '''granuloma'''.
** NOT a tumour, despite the suffix "-oma".
** A circumscribed sphere of chronic inflammatory cells enveloped by poorly organised attempts at encapsulation by local connective tissue.
* The differences between a granuloma and an abscess must be appreciated.
** The fibrous envelope is never as well developed as that of an abscess.
** The inner contents are never as completely fluid as in an abscess.
==Structure of a Granuloma==
===Central core===
* The central core which contains the agent.
* The agent may be visible with H&E staining in section, e.g.
** ''[[Actinobacillus lignieresii]]''
*** The cause of "Wooden tongue" in cattle.
*** Appears as a granule, with a central core of the bacterial colony surrounded by radiating eosinophilic "clubs".
**** Clubs are considered to be formed from degenerating collagen and antigen-antibody complexes.
** ''[[Actinomyces bovis]]''
*** The cause of "Lumpy Jaw" in cattle.
*** Forms granules containing bacteria and "clubs".
** Fungal hyphae
** Parasitic larvae
** Foreign bodies
* The agent might not be visible without being selectively stained.
** E.g. [[:Category:Mycobacterium species|''Mycobacterium tuberculosis'']] and ''[[Brucella abortus]]''.
*** Stain using an acid-fast stain (Ziehl-Neelsen), or a modification.
*** These organisms are intracellular in the macrophages.
===Chronic Inflammatory Cells===
* Outside the core is a substantial number of chronic inflammatory cells.
** Mainly macrophages.
*** Often appear as epithelioid cells.
** Lymphocytes
** Plasma cells.
* Neutrophils and necrotic remnants of cells can be quite prominent in the granulomas of [[:Category:Actinobacillus species|''Actinobacillus'']] and [[:Category:Actinomyces|''Actinomyces'']] species.
* Eosinophils are prominent in parasitic granulomas.
* A scattered and variable number of Giant cells are often seen, but not always in every granuloma.
===Outer Envelope===
* The final layer is an outer envelope of incomplete fibrous tissue.
* Giant cells can also be seen in this area.
==Gross Appearance of Granulomas==
* The cut surface of granulomas varies considerably;
** Tuberculous granulomas tend to have solid whitish cores which are often calcified.
*** Grate on the knife when cut through.
** Parasitic granulomas are often greenish in colour due to the substantial numbers of eosinophils.
*** Older ones are also often calcified.
** [[:Category:Actinobacillus species|''Actinobacillus'']] and [[:Category:Actinomyces|''Actinomyces'']] species often have liquefied cores due to the necrosis and [[Neutrophils|neutrophils]].
*** I.e. they are purulent.
*** May discharge to the surface along sinus tracts.
*** The central core of bacteria and ‘clubs’ may appear as yellowish granules in this pus.
**** Often called "sulphur granules".
[[Category:Chronic Inflammation]][[Category:To Do - Blood]]