The patient presented with a history of a right leg rash, which resolved, and lesions on his forearm. His past history is significant for non-necrotizing granulomas of the lung.
Case Discussion
Granuloma annulare (GA) is an inflammatory dermatosis that usually occurs in children and young adults, and is more common in females. It usually presents with annular papules on the upper and lower extremities. GA can clinically present in a variety of ways; localized GA (most common), generalized GA, subcutaeous GA, perforating GA, and patch GA.
On microscopy, GA can have two patterns: palisading or interstitial. Dermal histiocytes and perivascular lymphocytes are present in both patterns. The palisading pattern is characterized by areas of degenerated collagen and mucin surrounded by palisading histiocytes mixed with lymphocytes. In the interstitial pattern, the histiocytes are infiltrating between collagen bundles in the dermis, and the necrobiosis and stromal mucin may be more subtle. Special staining for Hale's colloidal iron and Alcian blue can be used to highlight the dermal mucin.
This slide shows Alcian blue stain. See Related Content for H&E stain.
Diaconescu, ED., Sade, S. Skin, granuloma annulare, Alcian blue stain. Digital Laboratory Medicine Library, Dept of Laboratory Medicine & Pathobiology, University of Toronto. Published
. Accessed December 17, 2025. https://dev.dlml.cflabs.ca/image/skin-granuloma-annulare-alcian-blue-stain-lmp15239
