Eccrine poroma: causes, symptoms, diagnosis, treatment

The term "eccrine poroma" was first proposed by H. Pinkus et al. (1956) to denote a benign tumor histogenetically associated with the intraepidermal portion of the sweat gland duct, the so-called acrosyringium.

Symptoms of eccrine poroma. The tumor occurs mainly on the skin of the extremities, although the localization can be very different. The average age of patients is 67 years. It is assumed that the ratio of patients of different sexes is approximately equal or there is some predominance of men. The duration of the tumor is from several months to 10 years or more. The tumor is predominantly solitary, less often multiple. Usually the tumor occurs on intact skin, however, there are observations of the occurrence of poroma against the background of chronic post-radiation dermatitis.

Clinically, the tumor appears as a skin-colored nodule no more than 1-2 cm in diameter with a smooth, shiny surface and telangiectasias. The color is pale pink or dark red, sometimes dark brown. The tumor surface may be scaly, papillomatotic, and have uneven hyperkeratosis. G. Burg (2000) observed a pore in the form of an exophytic lobular node with areas of erosion.

Pathomorphology of eccrine poroma. The tumor consists of solid growths or anastomosing strands of monomorphic, small, basaloid cells with basophilic nuclei and moderately expressed pale or slightly basophilic cytoplasm. The cells are connected by intercellular bridges. Within the layers of tumor cells, ductal structures with PAS-positive cuticle and cystic expansions are found. Small foci with signs of keratinization, layers of connective tissue with loans and lymphohistiocytic infiltration are observed.

Histochemically, tumor cells contain enzymes typical of eccrine differentiation cells, such as phosphorylase and succinate dehydrogenase, as well as glycogen, as in the epithelial cells of the ducts of embryonic eccrine glands.

Electron microscopy revealed that the bulk of tumor cells had clear signs of squamous epithelium. The cytoplasm contained bundles of tonofilaments, and the plasma membranes formed narrow, thin plasmatic outgrowths that contacted similar outgrowths of neighboring cells with the help of numerous desmosomes. Concentrically located cells formed duct structures, on the luminal surface of which numerous short, densely located microvilli were visible. Quite characteristic was the presence of squamous epithelial cells with intracytoplasmic ducts located centrally, with microvilli lining the lumen and surrounded by thick bundles of tonofilaments.

Histogenesis. The connection between vice and acrosyringium is confirmed by the above histological, histochemical and ultrastructural data.

Eccrine poroma is differentiated primarily from seborrheic keratoma. Unlike the latter, poroma does not contain horny cysts and melanin. Eccrine poroma differs from basalioma by the absence of palisade-like structures characteristic of basalioma, the presence of intercellular bridges and characteristic enzyme activity typical of eccrine structures.

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