Bilateral Facial Apocrine Fibrosing Hamartoma Mimicking Microcystic Adnexal Carcinoma.

An otherwise healthy 50-year-old woman was evaluated for the presence of 2 erythematous, and slightly pruritic plaques, involving both cheeks for 30 years. Left-side skin biopsy showed a diffuse proliferation of ductal structures horizontally arranged and involving the reticular dermis that resembled tubular adenoma embedded in a sclerotic stroma and surrounded by a peculiar periductal desmoplasia. Nuclear atypia or mitosis was not found. Contralateral biopsy showed identical findings. Differential diagnosis included microcystic adnexal carcinoma (MAC) and plaque-like syringoma and a peculiarly horizontally arranged tubular adenoma. We ruled out MAC as the lesions were long-standing, without infundibular cysts, solid strands, or perineural infiltration. Our case closely resembled those previously described as sweat duct proliferation associated with aggregates of elastic tissue and atrophoderma vermiculatum, although striking differences were observed, as our case did not present aggregates of elastic tissue, did not involve the papillary and superficial reticular dermis, and presented evidences of decapitation secretion as a sign of apocrine differentiation. We consider our case as a MAC simulator and we propose the descriptive name of bilateral facial apocrine fibrosing hamartoma.