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Case Reports

Abstract

A 69-year-old male presented with a polycyclic annular plaque on the forearm with a violaceous rim studded with keratotic papules, central atrophy, and background dermatoheliosis. Punch biopsy specimens demonstrated dilated follicular infundibula, prominent cystic invagination of the epidermis and pseudoepitheliomatous hyperplasia. Within the dermis were palisaded and interstitial granulomas with central necrobiosis and focal elastophagocytosis. The histopathologic findings were consistent with an inflammatory granulomatous dermatitis with features of actinic granuloma and associated regressed keratoacanthoma-like change. Keratoacanthoma and comedone-like changes associated with granulomatous dermatitis have rarely been described in the literature. These changes may mimic squamous cell carcinoma, potentially leading to surgical, instead of anti-inflammatory, management. Keratoacanthoma-like changes may occur as an attempt to extrude elastin via transepidermal elimination. Alternatively, it has been proposed that comedone formation may occur due to the presence of solar elastosis and elastophagocytosis and resultant loss of supportive connective tissue in the dermis. Dermatopathologists should be aware of reactive cystic pseudoepitheliomatous hyperplasia in the setting of granulomatous disorders to avoid a misdiagnosis of neoplasm.