Syringoma is a benign adnexal neoplasm formed by well-differentiated ductal elements. The name syringoma is derived from the Greek word syrinx, which means pipe or tube.
Based on Friedman and Butler’s classification scheme, 4 variants of syringoma are recognized: (1) a localized form, (2) a form associated with Down syndrome, (3) a generalized form that encompasses multiple and eruptive syringomas, and (4) a familial form.
Syringoma is generally considered a benign neoplasm that differentiates along eccrine lines.
Enzyme immunohistochemical tests demonstrate the presence of eccrine enzymes such as leucine aminopeptidase, succinic dehydrogenase, and phosphorylase. The immunohistochemical pattern of cytokeratin expression indicates differentiation toward both the uppermost part of the dermal duct and the lower intraepidermal duct (ie, sweat duct ridge). However, distinguishing between eccrine and apocrine ducts is sometimes difficult, and many tumors that were traditionally thought to be eccrine have been shown to have apocrine differentiation. Electron microscopy of syringomas demonstrates ductal cells with numerous short microvilli, desmosomes, luminal tonofilaments, and lysosomes.  The histogenesis of syringomas is most likely related to eccrine elements or pluripotential stem cells.
Some investigators have suggested that cases of eruptive syringoma may represent a hyperplastic response of the eccrine duct to an inflammatory reaction rather than a true adnexal neoplasm.  In this setting, these authors propose the term syringomatous dermatitis for such cases. Likewise, the scalp "syringomas" seen in scarring alopecia represent a reactive proliferation in response to the fibrosis.
Syringomas affect approximately 1% of the population.
A racial or ethnic predilection has not been reported.
Females are affected by syringomas more often than males.
Syringomas usually first appear at puberty; additional lesions can develop later.
Syringomas are benign and are largely of cosmetic significance. With treatment, syringomas ideally should be destroyed with minimal scarring and no recurrence. See Surgical Care.