Syringoma

Syringoma (syn.: multiple syringoadenoma, eruptive hidradenoma) is a developmental defect of the eccrine sweat gland, similar in its structure to the ductal section in the upper part of the dermis.

Epidemiology

The incidence of syringoma in patients with Down syndrome is 30 times higher than in the population of patients with other mental illnesses. Syringoma is a component of Nicolau-Balus syndrome (eruptive syringoma, miliary cysts, and vermiform atrophoderma). Syringoma is often combined with benign tumors or malformations of the skin.

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Pathogenesis

In the superficial and middle sections of the dermis there are a large number of small and medium-sized cysts of round or oval shape, lined with two layers of epithelial cells. The layer of cells adjacent to the basement membrane is flattened, their nuclei are intensely stained; the layer facing the cyst cavity consists of lighter cubic or prismatic cells. The contents of the cysts are homogeneous or slightly granular.

In addition to cysts, syringoma contains thin strands of small cells with dark nuclei. Some strands are cystically dilated at one pole, resembling tadpoles in shape, which is typical for this tumor. Cysts lined with stratified squamous epithelium and filled with layered masses of keratin may be observed. These cysts sometimes rupture, their contents enter the dermis, causing a giant cell reaction, and then calcify. Sometimes in syringoma cysts, pronounced proliferation of lining cells is observed with the formation of solid strands growing through the basement membrane - syringocystadenoma. The tumor stroma is mostly unchanged, but sometimes lymphohistiocytic infiltrates are found in it. In addition to the usual variant of the histological structure, a clear cell variant of syringoma has been described.

Histochemical examination reveals the activity of enzymes characteristic of eccrine glands - succinate dehydrogenase, phosphorylase and leucine aminopeptidase, while lysosomal enzymes characteristic of apocrine structures (acid phosphatase and beta-glucuronidase) are very weakly detected. The clear cell variant of syringoma is characterized by a high glycogen content. Electron microscopy reveals microvilli, quite a lot of lysosomes and tonofilaments in the cells lining the tubular structures.

Histogenesis of syringoma

There are different points of view on the histogenesis of syringoma. Some authors, based on histochemical and electron microscopic data, believe that this tumor has an eccrine differentiation, while localization in places of accumulation of apocrine glands, rash of elements mainly in the pubertal period and histotopic connection with immature hair follicles and sebaceous glands do not exclude apocrine genesis in some cases

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Symptoms syringomas

The tumor is often multiple, located symmetrically on the face, especially in the eyelid area, on the chest, less often in other places. It develops more often in women during puberty, familial cases have been described. In addition, limited localization of syringoma on the vulva, penis, proximal phalanges of the hands has been described. Syringoma localized on the scalp may be accompanied by diffuse alopecia.

The multiple variant of syringoma is represented by small nodules, slightly protruding above the surface of the skin, slightly shiny, as if translucent or yellowish.

Differential diagnosis

Differential diagnosis of syringoma is quite simple and is based on the presence of multiple small cysts and tadpole-like ductal structures.

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