Background
Syringoma is a benign adnexal neoplasm formed by well-differentiated ductal elements. The name syringoma is derived from the Greek word syrinx, which means reed or pipe.
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.
Pathophysiology
Syringoma is generally considered a benign neoplasm that differentiates along eccrine lines; very rare malignant variants (syringocarcinoma) are described.
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. [1] 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. [2] In this setting, the term syringomatous dermatitis may be more appropriate. Likewise, the scalp “syringomas" seen in scarring alopecia represent a reactive proliferation in response to the fibrosis.
Etiology
Syringomas are usually sporadic, but more than 10 cases of familial syringomas have been reported in the English literature. In the familial setting, syringomas tend to occur in preadolescence or adolescence, most commonly affect the face, and are usually inherited as an autosomal dominant trait. [3]
Eruptive syringomas (see image below) are more common in African Americans and Asians than in other ethnic groups. One patient presented with extensive eruptive syringomas following liver transplantation, suggesting a potential role for immunosuppression in pathogenesis. [4]
In Down syndrome, the prevalence of syringoma is reportedly approximately 18-40%, usually located in the periorbital region; however, rare cases of widespread eruptive syringomas associated with Down syndrome have also been reported. [5, 6, 7] Syringomas associated with Down syndrome have a higher rate of calcification, which may progress to calcinosis cutis. [8]
Some cases of syringoma are associated with diabetes mellitus; altered glucose metabolism perhaps may lead to the clear-cell phenotype of syringomas in the setting of diabetes. [8, 9]
Epidemiology
Frequency
Syringomas affect approximately 1% of the population.
Race
A racial or ethnic predilection has not been reported.
Sex
Females are affected by syringomas more often than males.
Age
Syringomas usually first appear at puberty; additional lesions can develop later.
Prognosis
Syringomas are benign and their significance is largely cosmetic. With treatment, syringomas ideally should be destroyed with minimal scarring and no recurrence. See Surgical Care.
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The multiple, small, yellow papules in the lower lid and upper part of the cheek correspond to syringomas. The blue cyst in the inner canthus is an eccrine hidrocystoma. Courtesy of Mark S. Brown, MD, University of South Alabama Medical Center.
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Eruptive syringomas.
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Histologic section of syringoma demonstrates numerous small ducts in a sclerotic stroma. Note the tadpole-shaped ducts.
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Histologic section of clear-cell syringoma.
