Page 180 - Textbook of Pathology, 6th Edition

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SECTION I

Figure 6.37 Actinomycosis. Microscopic appearance of sulphur granule lying inside an abscess. The margin of the colony shows hyaline
filaments highlighted by Masson’s trichrome stain (right photomicrograph).

granules. The infection may extend into adjoining soft ETIOLOGY AND PATHOGENESIS. The cause of
tissues as well as may destroy the bone. sarcoidosis remains unknown. Currently, possible etiology
2. Thoracic actinomycosis. The infection in the lungs is is an infectious or noninfectious environmental agent in a
due to aspiration of the organism from oral cavity or genetically susceptible individual. Likely infectious agents
extension of infection from abdominal or hepatic lesions. include Propionibacter acnes, atypical mycobacteria and
Initially, the disease resembles pneumonia but mycobacterial protein of M. tuberculosis. Since the disease is
subsequently the infection spreads to the whole of lung, characterised by granulomatous tissue reaction, possibility
pleura, ribs and vertebrae. of cell-mediated immune mechanisms has been suggested.
3. Abdominal actinomycosis. This type is common in The following observations point towards a possible immune
appendix, caecum and liver. The abdominal infection origin of sarcoidosis:
General Pathology and Basic Techniques
results from swallowing of organisms from oral cavity or 1. Just as in tuberculosis, sarcoidosis is characterised by
extension from thoracic cavity. distinctive granulomatous response against poorly degradable
4. Pelvic actinomycosis. Infection in the pelvis occurs antigen, but quite unlike tuberculosis, the antigen in
as a complication of intrauterine contraceptive devices sarcoidosis has eluded workers so far. PCR studies on
(IUCD’s). affected pulmonary tissue have given equivocal result as
regards presence of mycobacterial antigen.
Microscopically, irrespective of the location of actino- 2. There are immunologic abnormalities in sarcoidosis is
mycosis, the following features are seen (Fig. 6.37): substantiated by high levels of CD4+T cells lavaged from lung
i) The inflammatory reaction is a granuloma with central lesions. There is also elevation in levels of IL-2 receptors in
suppuration. There is formation of abscesses in the centre serum and in lavaged fluid from lungs.
of lesions and at the periphery chronic inflammatory cells,
giant cells and fibroblasts are seen. 3. There is presence of activated alveolar macrophages which
ii) The centre of each abscess contains the bacterial elaborate cytokines that initiate the formation of non-
colony, ‘sulphur granule’, characterised by radiating caseating granulomas.
filaments (hence previously known as ray fungus) with MORPHOLOGIC FEATURES. The lesions in sarcoidosis
hyaline, eosinophilic, club-like ends representative of are generalised and may affect various organs and tissues
secreted immunoglobulins. at sometime in the course of disease, but brunt of the
iii) Bacterial stains reveal the organisms as gram-positive disease is borne by the lungs and lymph nodes (Fig. 6.38).
filaments, nonacid-fast, which stain positively with Microscopically, the following features are present
Gomori’s methenamine silver (GMS) staining. (Fig. 6.39):
1. The diagnostic feature in sarcoidosis of any organ or
SARCOIDOSIS (BOECK’S SARCOID)
tissue is the non-caseating sarcoid granuloma, composed of
Sarcoidosis is a systemic disease of unknown etiology. It is epithelioid cells, Langhans’ and foreign body giant cells
worldwide in distribution and affects adults from 20-40 years and surrounded peripherally by fibroblasts.
of age. The disease is characterised by the presence of non- 2. Typically, granulomas of sarcoidosis are ‘naked’ i.e.
caseating epithelioid cell granulomas (‘sarcoid granuloma’) either devoid of peripheral rim of lymphocytes or there is
in the affected tissues and organs, notably lymph nodes and paucity of lymphocytes.
lungs. Other sites are the skin, spleen, uvea of the eyes, 3. In late stage, the granuloma is either enclosed by
salivary glands, liver and bones of hands and feet. The hyalinised fibrous tissue or is replaced by hyalinised fibrous
histologic diagnosis is generally made by exclusion. mass.