Characterizing the nature of eccrine syringofibroadenoma: illustration with a case showing spontaneous involution.

Eccrine syringofibroadenoma (ESFA) is a histological entity. It has been widely debated as to whether ESFA is a true neoplasm, a hamartoma or a form of reactive hyperplasia. ESFA should not be considered a homogenous condition and there are five clinical subtypes: (i) multiple ESFA associated with ectodermal dysplasia, (ii) multiple ESFA without cutaneous features (both hamartomatous), (iii) unilateral linear ESFA (naevoid), (iv) solitary ESFA (neoplastic) and (v) reactive ESFA, which seems to start off as pathologically hyperplastic and then become hamartomatous. We report a patient with reactive ESFA secondary to lepromatous leprosy, showing spontaneous involution in an area of her lesions. Reactive ESFA represents a hyperplastic and hamartomatous process, and may be more appropriately known as reactive eccrine syringofibroadenomatosis. The risk of malignancy is low in reactive ESFA, and monitoring instead of excision is a reasonable option.