Abstract

Dermatofibromas are common benign skin tumors characterized by fibrohistiocytic proliferation within the dermis, often with overlying epidermal acanthosis and collagen trapping at the periphery. Several histologic subtypes are recognized, including, but not limited to, aneurysmal, cellular, and hemosiderotic. In 2005, a report of two lesions demonstrating apocrine gland cysts with surrounding hemosiderotic dermatofibroma-like stroma was described in the literature. Subsequently, in 2013 the term adenodermatofibroma was proposed and the lesion recognized as a subtype of dermatofibroma. Fewer than 10 cases of this variant have since been reported. We present here the case of a 69-year-old female with history of melanoma and multiple non-melanoma skin cancers, as well as, immunosuppression status post kidney transplant, who presented with a violaceous, minimally firm, asymptomatic, lobular plaque on the right buttock that had been present for 20 years. The lesion was excised, and microscopic examination demonstrated intradermal cystic spaces lined by a single or double layer of cuboidal cells surrounded by a cellular fibrohistiocytic proliferation, compatible with an adenodermatofibroma. Our case highlights a rare newly described variant of an otherwise common skin tumor characterized by the unusual presence of dilated glandular structures embedded within the typical fibrohistiocytic stroma. Given the paucity of reported cases, there remains discussion regarding the derivation of the glandular structures. Proposed theories include the induction of apocrine glands by the dermatofibroma or entrapped eccrine units with apocrine metaplasia, with the latter being somewhat favored in recent literature, due to many of the lesions presenting at sites where apocrine glands are not typically present.

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