Definition: Syringoma is considered a benign neoplasm of the eccrine ducts in the skin.
Etiology: For most cases the etiology is unknown. Loss of heterozygosity of the familial gene for cylindromatosis has been reported at 16q or 16p in sporadic cases of syringoma. Familial cases of syringoma have been reported but are rare. Cases of eruptive syringomas have occurred in association with Down's syndrome (18-64%). Syringomas are part of the Nicolau-Balus syndrome (syringoma, milia, atrophodermis vermicula).
Incidence/Prevalence: Eruptive syringoma occurs with a frequency of 1/2500 in surgical biopsies.
Clinical: Click to enlarge photo.
Syringomas usually appear in crops on the patient's face especially the lower eyelids and are more common in women at puberty and beyond. For a clinical photograph please click
here.
The lesions are soft in texture, similar in color to the normal skin or slightly yellow and measure about 1-2 mm in size.
Histopathology: 
Click on pictures for larger image. Identify the structures at the numbered arrows.
Both photographs feature ductular structures (1) and more solid appearing nests and strands (2) that are present within the dermis. Occasionally the ducts have solid extensions that have been likened to a comma in shape (3 below).
The ductular structures (1) are lined by bland cells with amphophilic cytoplasm (clear due to glycogen) and there is an eosinophilic lining internally and occasionally externally. The material in the lumen of the ducts (1) is keratinaceous. These structural features recapitulate the eccrine sweat gland apparatus.
A malignant syringoma, also known as sclerosing sweat duct carcinoma has been described in the eyelids.
