Syringoma Workup

Updated: Mar 27, 2019
  • Author: Christopher R Shea, MD; Chief Editor: Dirk M Elston, MD  more...
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An adequately deep biopsy is required to rule out microcystic adnexal carcinoma. Clinical follow-up with consideration of rebiopsy for persistent or recurrent lesions is indicated.


Histologic Findings

Syringoma is usually located mostly in the superficial dermis and is composed of numerous small ducts embedded in a sclerotic stroma (see image below). Rarely, deep reticular dermal involvement has been reported. [23]

Histologic section of syringoma demonstrates numer Histologic section of syringoma demonstrates numerous small ducts in a sclerotic stroma. Note the tadpole-shaped ducts.

The walls of the ducts are usually lined by two rows of cuboidal-to-flattened epithelial cells and have a lumen containing periodic acid-Schiff–positive, eosinophilic, amorphous debris. Some of the ducts have elongated “tails” of epithelial cells, producing a characteristic comma-shaped or tadpole appearance. Rarely, tumor cells may appear clear as a result of glycogen accumulation (see image below).

Histologic section of clear-cell syringoma. Histologic section of clear-cell syringoma.

In a research context, enzyme immunohistochemical tests in syringoma demonstrate the presence of eccrine-related 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). [24] Distinguishing between eccrine and apocrine ducts may be difficult, however.

The histologic differential diagnosis includes sclerosing (morphealike) basal cell carcinoma and desmoplastic trichoepithelioma. Importantly, syringoma must be distinguished from microcystic adnexal carcinoma, which has similar histologic features but tends to infiltrate the deep dermis and subcutaneous tissue. Therefore, partial superficial biopsies may be problematic in this situation.

Chondroid syringoma is a different benign adnexal tumor with a characteristic myxoid cartilaginous matrix and is analogous to the benign mixed tumor (pleomorphic adenoma) of salivary gland.