Porocarcinoma is a rare malignant dermal tumor originating from the cells of the ducts of the eccrine sweat glands. It can occur on unaltered skin or develop against the background of ecrinic poroma. The lower extremities are most often affected, porocarcinomas of the trunk, face and scalp are less common, and the upper extremities suffer even less often. It is a node on a wide base. Areas of ulceration may be detected on the surface of the node. Porocarcinoma is characterized by a relatively benign course. In the later stages, it can give lymphogenic and hematogenic metastases. It is diagnosed on the basis of histological examination. The treatment is operative.
Porocarcinoma (malignant eccrine poroma, epidermotropic eccrine carcinoma) is a very rare malignant neoplasm and, at the same time, the most common type of oncological lesion of the eccrine sweat glands. In 30-50% of cases, it is formed as a result of malignancy of benign eccrine poroma. The literature describes cases of porocarcinoma diagnosed at the age of 12 to 92 years. The tumor more often affects elderly patients, the average age of onset of symptoms of the disease is 67-68 years. Men and women suffer equally often.
In 45% of cases, porocarcinoma is found in the lower extremities. In 20% of cases, the skin of the trunk suffers, in 15% – the skin of the face and scalp, in 10% – the skin of the upper extremities. When located on the lower extremities, porocarcinoma is most often detected in the area of the soles, when localized on the upper extremities – in the area of the palms. Regional metastases are detected in 20-30% of patients with a newly diagnosed diagnosis and in 75% of patients with local relapses. Distant metastasis is possible. In the early stages, the course of porocarcinoma is relatively benign, with the appearance of secondary foci, there is a significant deterioration in the prognosis. The treatment is carried out by specialists in the field of oncology and dermatology.
The causes of porocarcinoma have not been reliably clarified. It has been established that the tumor often occurs as a result of the malignancy of eccrine pores. There are data on the development of neoplasms against the background of sebaceous nevus, actinic keratosis, sarcoidosis, the extramammary form of Paget’s disease, chronic lymphocytic leukemia, pernicious anemia and Hodgkin’s disease. Experts note that porocarcinoma can occur after traumatic injuries or receiving a high dose of X-rays. Possible associations of neoplasia with oncological diseases of internal organs.
Macroscopically, porocarcinoma is an exophytically growing node on a wide base. Microscopy of neoplasms in the thickness of the epidermis reveals nests of small basaloid cells with inclusions of larger cells with signs of atypia or alternating nests of basaloid cells and structures consisting of atypical cells. Atypical porocarcinoma cells have polymorphic hyperchromic nuclei. Sometimes single large cells are diffusely located in the unchanged epidermis, which is why the histological picture of porocarcinoma may resemble Paget’s disease.
In clusters of atypical cells, duct-like structures, areas of necrosis, small cavities and “horny pearls” can be viewed. Signs of infiltration are visible around the cell clusters. With the long-term existence of porocarcinoma, atypical cells can penetrate into the dermis, nearby hair follicles, perineural spaces, walls of blood and lymphatic vessels. During the immunohistochemical study, a positive reaction with alpha-lactatalbumin antigen, epithelial membrane antigen and carcinoembryonic antigen is determined.
Symptoms and diagnosis
Initially, a papule forms on the surface of the skin in the affected area. Subsequently, the papule transforms into a dense elastic or soft node rising above the surface of the skin. Most porocarcinomas are located on a wide base, nodes on the leg are less often detected. Some neoplasms have a lobular structure. The color of porocarcinoma varies from pinkish to dark red or red-brown. The size usually does not exceed 1-2 cm. The surface of neoplasia is smooth, sometimes there are signs of papillomatosis or minor hyperkeratosis. Some patients have marked tumor pigmentation.
In the initial stages, porocarcinoma is painless. With progression, ulceration, increased bleeding, itching and pain in the area of the neoplasm are possible. The probability of metastasis correlates with the size of porocarcinoma, large nodes metastasize more often than small ones. With lymphogenic metastasis, an increase in lymph nodes is observed, with hematogenous metastases, the clinical picture of the disease is supplemented by signs of dysfunction of the corresponding organs. Secondary foci of porocarcinoma can be detected in the lungs, liver, mammary glands, ovaries, bladder, mediastinum, peritoneum and retroperitoneal space. In the later stages of the disease, asthenization, weight loss, hyperthermia and other common signs of cancer are noted.
The dermatologist makes the diagnosis of porocarcinoma on the basis of clinical symptoms, histological and immunohistological examination data. Differential diagnosis of porocarcinoma is carried out with a wart, seborrheic keratosis, trichoepithelioma, amelanotic melanoma, squamous cell skin cancer and basal cell carcinoma. To detect lymphogenic metastases, ultrasound of regional lymph nodes is performed. To detect hematogenic secondary foci of porocarcinoma, chest x-ray, ultrasound of the abdominal cavity and retroperitoneal space, ultrasound of the pelvic organs, MRI of the liver and other studies are prescribed.
Treatment and prognosis
The treatment of this pathology is operative. Porocarcinoma is excised together with the surrounding unchanged tissues, the material is transferred to the laboratory for urgent intraoperative histological examination. If atypical cells are detected in the incision area, the volume of surgical intervention is increased. When a defect is formed after the removal of porocarcinoma, skin plasty is performed.
The prognosis for porocarcinoma is determined by the size and localization of the tumor. According to studies, metastasis is observed with a neoplasia diameter of more than 2.8 cm. Neoplasms in the foot area recur in 24% of cases, on the lower leg – in 16% of cases, on the hip – in 8% of cases. Relapses of porocarcinoma can occur within a period of 4 months to 10 years from the moment of excision of the primary focus. In 75% of cases with relapse, lymphogenic metastases are detected. Lymphogenic metastasis (both in newly diagnosed neoplasias and in recurrent processes) in 68% of cases ends in death. With porocarcinomas with a diameter of less than 1 cm, no deaths were recorded.