A Systematic approach to diagnose Cutaneous Infections by Dermatopathologists
- Suppurative granuloma:
Image of suppurative granuloma
1) Lepromatous leprosy - Hematoxylin and eosin stain. ; 2) Ziehl Neelsen staining showing the lepra bacilli. 3)Malakoplakia 4) Parasitized macrophages in Leishmaniasis
2) Type of inflammatory cellular infiltrate:
- Prominence of plasma cells: Syphilis
- Prominence of eosinophils: Arthropod bite, helminth infestation.
- Prominence of neutrophils:
- Presence of histiocytes and plasma cells:
- Presence of parasitized macrophages and parasitized multinucleated giant cells:
i) Presence of parasitized macrophages: Rhinoscleroma
ii) Parasitized multinucleated giant cells: fungal infection.
3. Changes in the epidermis:
- Psoriasiform epidermal hyperplasia: Chronic candidosis
4. Changes in the Dermis and Cutaneous Appendages:
- Superficial and deep dermal perivascular inflammatory infiltrate
- Vasculitis: Necrotizing fasciitis, erythema nodosum leprosum, meningococcal and gonococcal septicemia, rickettsial infections, cytomegalovirus infection, recurrent herpes.
5. Spindle cell pseudotumour:
6. Invisible dermatoses:
Section appears almost normal when stained with Hematoxylin and eosin stain Dermatophytosis, Pityriasis versicolor ; Erythrasma.
Identification of fungi in tissue section:
- Periodic Acid Schiff with or without diastase is the most commonly used special stain. Cell wall stains purple with Periodic Acid Schiff.
Cryptococcus is stained with mucicarmine stain or a combined alcian blue- Periodic Acid Schiff stain. The cell wall and the capsule appear in contrasting colour.
- Silver methenamine stain (Grocott's method). Stains fungi black against green backround. It is more reliable than Periodic Acid Schiff for detecting degenerate fungal organisms.
- Gomori methenamine silver with Hematoxylin and Eosin counterstain demonstrate fungi and tissue components simultaneously.
- Calcofluor white used to stain frozen or paraffin sections and viewed with a fluorescence microscope.
- Polymerase chain reaction (PCR) technique :
Used to identify specific species of fungi.
Histochemistry in identification of microorganisms in skin sections:
- Pyodermas (impetigo and its variants and ecthyma) - Cocci demonstrated by Gram stain
- Erythrasma - small coccobacilli in stratum corneum- Gram stain, Periodic Acid Schiff and methenamine silver positive.
- Tuberculosis and non-tuberculous (atypical) mycobacterial.
Acid fast bacilli identified by Ziehl Neelsen stain.
- Leprosy - Hematoxylin-eosin and Fite Faraco staining method on tissue section are sufficient for evaluation.
Sometimes Gomori - methenamine silver stain help to detect remnants of Mycobacterium Leprae in treated patients.
- Histioid Leprosy - Acid fast bacilli arranged parallel to long axis of cell.
- Rhinoscleroma - Periodic Acid Schiff, Gram and Warthin starry stains positive.
- Malakoplakia - Periodic Acid Schiff positive diastase resistant inclusions. Calcospherites (Michaelis Gutmann bodies) are Von Kossa - positive.
- Rickettsia- Organisms demonstrated in endothelium or vessel wall using fluorescein-labelled antisera or with immunoperoxidase techniques.
- Spirochaete -Treponema pallidum and its subspecies are demonstrated by silver impregnation technique - Levaditi or Warthin-Starry.
- Actinomycosis - Granules are composed of slender filaments - Gram and Periodic Acid Schiff positive and stains grey or black with silver methenamine.
Not acid fast.
Club shaped bodies at the periphery and matrix of granules are Gram negative.
- Nocardiosis - Gram positive & weakly acid fast. Also stains with silver methenamine.
- Leishmaniasis - Leishman-Donovan bodies are better identified in sections stained with Weigert iron hematoxylin than those stained with hematoxylin and eosin or the Giemsa stain.
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