Granulomatous Dermatitis

Granulomatous dermatitis is a nodular or diffuse inflammatory pathologic process that is composed predominantly of histiocytes. The reaction pattern forms in response to an antigen that is usually insoluble, nondegradable, or slowly released.

Deciding whether a pattern is perivascular, interstitial, nodular, or diffuse is rather subjective. A pattern is considered nodular when discrete perivascular inflammation extends beyond a single perivascular region and is relatively large and dense. One or more nodules may be present. Diffuse dermatitis is the term applied when the cellular infiltrate is dense enough that discrete cellular aggregates cannot be recognized and the dermis contains a more massive poorly circumscribed inflammatory infiltrate. The dermal infiltrate can be uniformly dense or denser in the upper (or lower) dermis. Once the pattern has been recognized on scanning magnification, the patterns are subdivided by inflammatory cell composition and the presence or absence of necrosis, foreign bodies, infectious organisms, epidermal hyperplasia, and so on.

The categories for granulomatous dermatoses are not absolute and are only useful as a skeletal framework from which to start one's interpretation of a histologic section. For example: (i) rarely cutaneous sarcoidosis may demonstrate tuberculoid granulomas or foreign body granulomas; (ii) cutaneous infections as tuberculosis or leprosy most commonly present as tuberculoid granulomas but can be sarcoidal or palisading in type; (iii) some infectious granuloma can be palisaded (as some fungal, mycobacterial infections and so on); (iv) foreign body granulomata can be nodular (sarcoidal, palisaded, or foreign body) or diffuse and mixed. Therefore, although pattern analysis is a helpful way to begin the evaluation of a slide, often evaluation of a granulomatous dermatitis must exceed routine light microscopy with hematoxylin-eosin staining.

Infectious agents may need to be excluded by special stains:

Organisms

Stains

Fungi/yeast*

PAS with and without diastase GMS (methenamine silver)

Mycobacteria*

Ziehl-Neelsen (detects tubercle bacillus)

Fite (detects leprosy bacillus and tubercle bacillus)

Bacteria*

Gram

Actinomycosis and Nocardiosis

Gram

GMS (methenamine silver)

Leishmaniasis

Giemsa

Spirochete

Warthin-Starry

Amoeba

Phosphotungstic acid hematoxylin

*Stains most commonly utilized: periodic acid-Schiff (PAS); Gomori methenamine silver (GMS).

*Stains most commonly utilized: periodic acid-Schiff (PAS); Gomori methenamine silver (GMS).

Polariscopic examination can be accomplished to investigate the presence of a polarizable foreign body. Using two disks composed of polarizing plastic that are easily inserted into the microscope (with one disk below the condenser to act as a polarizer and the other disk placed in the eyepiece to act as the analyzer) the light from all rays except those vibrating in one plane can be excluded. Doubly refractile substances on the slide will break the polarization when the analyzer disk is rotated and appear as bright white bodies on a dark field. Examples of doubly refractile foreign bodies include silica, talc, wooden splinters, suture, and urate crystals.

Immunohistochemical techniques using a panel of antibodies directed against infectious agents and the technique of polymerase chain reaction are now available to detect possible microorganisms within fixed tissue.

Finally, electron-probe microanalysis (scanning electron microscopy with the aid of backscattered electron imaging and X-ray energy spectrometry) or chemical analysis can be used to identify inorganic material in a lesion.

In summary, when reviewing a slide that demonstrates a granulomatous dermatitis, the following questions should be addressed in attempting to establish a diagnosis:

1. Is the infiltrate nodular or diffuse?

2. If the infiltrate is nodular, is the pattern tuberculoid, sarcoidal, palisaded, or foreign body in type?

3. Is there any evidence of necrosis or necrobiosis?

4. Are there other inflammatory cells present in addition to the histiocytic infiltrate (as lymphocytes, neutrophils, etc.)? Are there distinctive features to the histiocytes composing the infiltrate?

5. Is the infiltrate perifollicular?

6. Is there associated epidermal hyperplasia?

7. Is there an associated vasculitis?

8. Special stains and polarizing lenses should be used routinely to exclude an infectious etiology and polarizable foreign body. Immunohistochemical techniques and electron probe microanalysis are only employed rarely.

The histologic patterns of granulomatous dermatoses are given in Table 1.

Table 1 Histologic Patterns of Granulomatous Dermatoses

Nodular granulomatous dermatitis

Tuberculoid

Tuberculosis Tuberculoid leprosy Leishmaniasis, chronic cutaneous Syphilis, late secondary or tertiary Rosacea and perioral dermatitis

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Responses

  • belinda
    What are "refractile foreign bodies" lung?
    7 years ago
  • Sarah
    Is there a cure for granulomatous dermatitis with polarizable foreign body?
    6 years ago
  • FIORI
    How to treat granulomatous dermatitis with polarizable foreign body material?
    6 years ago

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