Pathology of granuloma annulare

Histology of granuloma cancel

The histology examination view of the granuloma annulare shows a granulomatous inflammatory pattern located within the superficial and middle dermis.

• Figure 1. Closer inspection reveals palisade of histiocytes around an approach of necrobiosis and increased mucin statement.
• Figure 2, Figure 3. The involved dermis appears normal. Multinucleate giant cells they are seen frequently.
• Figure 4. A slight perivascular and interstitial lymphocytic infiltrate can be seen in the surrounding dermis with scattered neutrophils and eosinophils. Plasma Cells are rare.
• Associated vascular fibrin deposition and nuclear powder suggestive of vasculitis It seems to be a rare find.

Histological variants of the granuloma annulare

Subcutaneous GA: In this variant, the inflammatory infiltrate is predominantly within the deep dermis and extends into the subcutaneous tissue (Figure 5, 6). Large areas of necrobiosis can be seen along with a greater number of eosinophils (Figures 7, 8, 9).

Mitotically active variant: While typical mitotic activity is low, a mitotically active variant is recognized that might otherwise cause concern about a proliferative injury. Caution is recommended in these cases to exclude epithelioid sarcoma as discussed below.

Perforating GA: Here it can be seen that the inflammatory infiltrate is eliminated through the epidermis through a channel formed between epidermal descents.

Disseminated GA: While histology may be identical to typical GA, the infiltrate may be sparse and retained within the papillary dermis. Lichen nitido is sometimes considered in these cases.

Interstitial GA: the low-power pattern is different, shows a 'busy dermis' and lacks necrobiotic and mucinous foci. High power reveals the interstitial infiltrate of benign Histiocytes appearing. Although less visible, an increase in mucin is often seen around the inflammatory infiltrate. In the presence of many eosinophils and interface changes, an interstitial granulomatous drug reaction should be considered.

Special spots in granuloma annulare

Mucin stains such as colloidal iron and alcian blue can be used to highlight the increase connective tissue mucins

Differential diagnosis of granuloma annulare

Lipoid necrobiosis: layered with open necrobiotic foci. Lacks mucin. An increased number of plasma cells may be a clue.

Rheumatoid nodule: The changes seen here are more similar to the subcutaneous variant of GA. The discriminatory characteristics observed in the rheumatoid nodule include the presence of larger areas of eosinophilic necrobiosis and lack of mucin deposition. The medical history is usually informative.

Epithelioid sarcoma: always think twice when diagnosing GA in the digits. While the low power pattern may be similar due to the eosinophilic areas of necrosisa closer inspection will always reveal a atypical infiltrate. Immunohistochemistry is definitive in difficult injuries that show Epithelial membrane antigen (EMA) and Cytokeratin (CK) positivity.