Patholgy Slides : Chronic inflammation
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Chronic inflammation is a long lasting inflammation (weeks or months) due to persistent aggressive stimuli and is characterized by: active inflammation with mononuclear cells, tissue destruction and repair. It can follow acute inflammation or can be chronic right from the beginning.
Types of chronic inflammation : unspecific (e.g. : chronic peptic ulcer) and specific (granulomatous).
According to the mechanism, granulomatous inflammation may be: immune type (tuberculosis, sarcoidosis) and non-immune type (foreign body reaction).
Classification of granulomatous inflammation, according to the etiology :
- Infectious granuloma :
- Bacterial :
- Mycobacterium tuberculosis (Koch bacillus) - Tuberculosis
- Mycobacterium leprae - Leprosy
- Treponema pallidum - Syphilis
- Gram-positive bacillus (Actinomyces israeli) - Actinomycosis
- Gram-negative bacillus (Bartonella henselae) - Cat-scratch disease
- Parasitic :
- Toxoplasma gondii - Toxoplasmosis
- Helminths - Cysticercosis
- Fungi (Candida albicans) - Candidiasis
- Bacterial :
- Foreign body granuloma
- Unknown etiology granuloma :
- Crohn's disease
Tuberculous lymphadenitis : tuberculous granuloma
Tuberculous lymphadenitis is a chronic specific granulomatous inflammation with caseation necrosis. The characteristic morphological element is the tuberculous granuloma (caseating tubercule) : giant multinucleated cells (Langhans cells), surrounded by epithelioid cells aggregates, T cell lymphocytes and few fibroblasts. Granulomatous tubercules evolve to central caseous necrosis and tend to become confluent, replacing the lymphoid tissue. (H&E, ob. x4)
Tuberculous granuloma. Multinucleated giant cell (mature - Langhans type) : 50 - 100 microns, numerous small nuclei (over 20) disposed at the periphery of the cell (crown or horseshoe), abundant eosinophilic cytoplasm. It results when activated macrophages merge. Epithelioid cells are activated macrophages resembling epithelial cells : elongated, with finely granular, pale eosinophilic (pink) cytoplasm and central, ovoid nucleus. They have indistinct shape contour and form aggregates. At the periphery are the lymphocytes (T cells) and rare plasma cells and fibroblasts. Caseous necrosis is a central area, amorphous, finely granular, eosinophilic (pink). If recent, it may contain nuclear fragments. The caseum is the result of giant cells and epithelioid cells destruction. (Hematoxylin-eosin, ob. x20)
Tuberculous granuloma (Hematoxylin-eosin, ob. x20)
Tuberculosis is a chronic inflammation caused by Mycobacterium tuberculosis (tubercle bacillus, Koch bacillus) - human type or bovine type. The most affected organ by tuberculosis is the lung. Microscopically, the characteristic lesion in tuberculosis is the tuberculous granuloma.
Pulmonary tuberculosis. Tuberculous granuloma is localized in the pulmonary interstitium, compressing the surrounding alveoli and destroing the parenchyma. (Hematoxylin-eosin, ob. x4) (For detailed histological description of granuloma
Tuberculous granuloma in the pulmonary interstitium. (Hematoxylin-eosin, ob. X20)
Tuberculous granuloma in the pulmonary interstitium. (Hematoxylin-eosin, ob. x20)
Foreign body granuloma
Foreign body granuloma has a non-immune mechanism. Foreign body granuloma is a reaction to exogenous materials (talc, suture material, parasites, oil droplets, wood, metals, silica, silicon) or endogenous (hail shafts, keratin, cholesterol, urates/goutous tophi), which are immunologically inert.
Microscopically, foreign body granuloma to suture material (nylon, silk) contains multinucleated giant cells, with haphazardly arranged nuclei. These giant cells are fused macrophages. The foreign body is birefringent, and sometimes may be visible by polarized light in the middle of the granuloma or inside the giant cells. These granulomas are non-necrotic. (HE, ob. x4)
Foreign body granuloma (suture material) (HE, ob. x10).