Which histologic findings are characteristic of subcutaneous granuloma annulare lesions?

Updated: Oct 15, 2020
  • Author: Ruby Ghadially, MBChB, FRCP(C)Derm; Chief Editor: William D James, MD  more...
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In many cases of subcutaneous granuloma annulare, and in some dermal infiltrates, the centers of granulomas contain degenerated, homogeneous-appearing collagen and are deeply eosinophilic. In some sections, necrotic small vessels in the centers of palisaded foci are surrounded by nuclear dust. Presence of fibrinogen can be shown by direct immunofluorescence in the centers of palisaded granulomas. In perforating lesions, necrobiotic material is extruded through focal perforations. Epidermal hyperplasia at the edge of the perforation forms a pseudochannel communicating with an underlying necrobiotic granuloma.

Rare cases of nonnecrobiotic, sarcoidal, or tuberculoid granuloma annulare are also described.

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