Eccrine mucinous metaplasia associated with an apocrine cystadenoma

Mucinous metaplasia occurs uncommonly in cutaneous pathology, usually at specialized anatomic locations (genitalia, palms, and soles) and within restricted pathologic contexts (inflammation and trauma). Here, we report a unique case of eccrine mucinous metaplasia associated with an apocrine cystadenoma. A 13-year-old girl had an asymptomatic, 4-mm nodule on the chest. Histopathology demonstrated a typical apocrine cystadenoma in the upper and middle dermis. Adjacent to this lesion was a cluster of coiled eccrine secretory glands, of which the inner layer was almost entirely replaced by benign-appearing cells containing abundant, non-sulfated acid mucopolysaccharides. At 10 months' follow up, there was no recurrence. Our case demonstrates that, very uncommonly, mucinous metaplasia may be associated with a pathogenetically separate, adjacent proliferative adenomatous lesion, in this instance, an apocrine cystadenoma.