Pathology of Granuloma
AnnulareDr Sampurna Roy MD
Granuloma annulare (GA) is a benign
inflammatory, self-limiting granulomatous dermatoses that is seen in
both adults and children
Females are more commonly affected than males.
The lesions may involve skin and/or subcutaneous tissue.
The etiology of granuloma annulare is unknown.
The lesions could be related to insect bites, sun exposure, viral infections, diabetes, thyroiditis, immunoglobulin-mediated vasculitis, and certain medications such as antibiotics, antiinflammatory agents and oral contraceptives.
Cases have also been reported in patients with AIDS, sarcoidosis, hepatitis C infection, Hodgkin's and non Hodgkin's lymphoma, metastatic adenocarcinoma and granulomatous mycosis fungoides.
(1) Localized - Children
and young adults. Papules and annular or arciform
(2) Generalized - Middle aged and elderly patients. Multiple macules,
papules or nodules.
(3) Perforating - Middle aged
and elderly females. Papules and annular
plaques. Scaling and crusting with central umbilication may be present.
(4) Subcutaneous or deep form - Children
and young adults. Solitary or
multiple nodules (a few millimeters to several centimeters in size).
Histological patterns in Granuloma Annulare:
1. Necrobiotic granuloma
2. Interstitial or 'incomplete' form - Most common
3. Granuloma of sarcoidal or tuberculoid type - Rare
Features of interstitial or 'incomplete' form of Granuloma Annulare:
- Should be assessed under low power.
- "Busy dermis" - increased number of inflammatory cells in the dermis separated by connective tissue mucin.
- Infiltrate composed of lymphocytes and histiocytes.
- Inflammatory cells are noted around blood vessels and between collagen bundles.
- No well-defined areas of necrobiosis
(1) Interstitial Granulomatous Drug Reaction: Eosinophils (+) , lichenoid changes at dermoepidermal junction , true necrobiosis is rarely noted .
(2) Interstitial Granulomatous Dermatitis: Neutrophils, neutrophil fragments, histiocytes, lymphocytes and eosinophils are present , palisades of histiocytes around basophilic collagen fibres.
Changes may involve the full thickness of the dermis.
Features of Subcutaneous Granuloma Annulare- (Pseudorheumatoid Nodule):
- Located in the deep dermis, subcutis and rarely deep soft tissue.
- Area of necrobiosis is larger than the superficial type.
- Granulation tissue and lymphoid aggregates may be present near palisaded granuloma.
- Eosinophils are more common in this variant.
Differential diagnosis: Rheumatoid Nodule : Rheumatoid nodule and subcutaneous granuloma annulare. A comparative histologic study.
Necrobiotic foci contain abundant fibrin. Degenerated bundles of collagen (+/-). Palisade of elongated histiocytes.
Features of disseminated form of granuloma annulare:
- Poorly formed granulomatous foci in the papillary dermis.
- Necrobiosis is not prominent.
Differential diagnosis: Lichen Nitidus : Claw-like acanthotic elongation of rete-ridges at the periphery of the lesion is absent in Granuloma annulare.
Non-necrobiotic sarcoidal or tuberculoid type of Granuloma annulare:
Dermal mucin and eosinophils help in distinguishing this lesion from sarcoidosis.
Epidermal perforation connected to the underlying necrobiotic granuloma.
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