Malignant eccrine poroma: causes, symptoms, diagnosis, treatment

Malignant eccrine poroma (syn.: porocarcinoma, epidermotropic eccrine carcinoma, eccrine porocarcinoma) is a very rare tumor, usually arising against the background of a long-standing eccrine poroma or de novo on unchanged skin. It usually occurs in elderly people, the average age of patients is 67 years, equally often in men and women. In 45% of cases, the tumor is localized on the skin of the lower extremities, in 20% - on the skin of the trunk, in 15% - on the head and in 10% - on the upper extremities. Rarely, porocarcinoma can have an unusual localization, in particular on the nail bed against the background of radiation dermatitis, or occur in a patient suffering from pigmented xeroderma.

Symptoms of malignant eccrine poroma

Clinically, it manifests itself as an exophytic node, the surface of which is eroded, on a broad base, with a diameter of 1-5 cm. Growth is relatively slow, with delayed metastasis to regional lymph nodes in 30%. In some cases, metastasis is accompanied by lymphostasis.

Pathomorphology is characterized by basaloid cell growths in the epidermis and cell complexes in the dermis. The intraepidermal component, unlike its benign counterpart, is represented by focal clusters of large cells with hyperchromatic, polymorphic nuclei, mitotic figures, and necrotic foci. Duct-like structures are sometimes visible in the tumor cell clusters. Intradermal complexes consist of light cells with large atypical nuclei containing coarsely dispersed chromatin. Slit-like or finely cystic cavities and orthokeratotic "horny pearls" are found among the cell growths. An inflammatory infiltrate is formed along the periphery of the tumor cords. Tumor cells are sometimes found in the lymphatic vessels of the dermis. The following histological variants can be observed with varying frequency in primary porocarcinoma: pagetoid cell type in hyperplastic epidermis; cells with clear cytoplasm with a high glycogen content; mucus foci in the stroma; perineural invasion. In clear cell variants, low phosphorylase activity was detected, which is associated with a deficiency of this enzyme in patients with diabetes mellitus, and this in turn leads to the accumulation of glycogen in tumor cells. Ultrastructural studies confirmed the squamous epithelial nature of the cells with the presence of tonofilaments, intertwined cytoplasmic villi, compacted junctions and intracytoplasmic lumens.

Histogenesis of malignant eccrine poroma. Porocarcinoma is a malignant tumor with differentiation of structures characteristic of the intraepidermal part of the eccrine sweat gland duct. In immunohistochemical examination, duct structures and keratinization foci give a positive reaction with carcinoembryonic AG, with AG of epithelial membranes and alpha-lactate talbumin antigen.

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