Melanoma is a malignant tumor that occurs as a result of atypical degeneration and reproduction of pigment cells (melanocytes). It most often affects the skin, but can also occur on mucous membranes. It is characterized by the rapid spread of tumor cells throughout the body. Melanoma is diagnosed according to the data of a smear-a fingerprint made from its surface. Histological confirmation of the diagnosis is made after the removal of the formation. Treatment is carried out depending on the stage of melanoma and may consist of surgical excision of the formation, removal of lymph nodes, immunotherapy, radiation therapy and chemotherapy.
Melanoma is a type of skin cancer. Melanoma accounts for 1-1.5% of all malignant neoplasms. According to WHO, about 48,000 people die from melanoma every year in the world and there is an increase in the incidence. Disease is most often diagnosed in patients living in southern countries in conditions of increased natural insolation. People over the age of 30 are mostly susceptible to the disease, but some cases of melanoma are also found in children. In various countries of the world, the incidence of skin melanoma varies from 5 to 30 people per 100,000 population.
The risk of developing melanoma is increased in individuals with skin type I and II. The development of the disease is most unlikely in people with dark skin and persons of the Negroid race. The likelihood of melanoma is increased by a history (even in early childhood) of sunburn, excessive ultraviolet radiation, both natural and obtained in a solarium. There is a hereditary predisposition — the occurrence of the disease in persons with a family history of cases of melanoma. Scientists suggest that this is due to a genetically transmitted disorder in the work of suppressors that suppress tumor growth.
About 70% of cases of melanoma development occur as a result of malignant degeneration of pigment nevi, which include: giant pigment nevus, blue nevus, Ota nevus, complex pigment nevus, borderline nevus. Xeroderma pigmentosa and Dubreuil melanosis can also transform into melanoma with a high probability. Factors triggering the process of malignancy of the nevus or pigment formation include its injury and increased insolation, hereditary and endocrine factors.
Modern dermatology classifies melanomas by phases of development and clinical types. There are two phases in the development of melanoma: horizontal and vertical. At the beginning of its development, melanoma grows only horizontally, without going beyond the epithelial layer. Then comes the vertical phase and the tumor process begins to spread into the lower layers of the skin, passes into the dermis and subcutaneous fat. In the vertical phase, the growth of melanoma accelerates significantly and its metastasis occurs.
Depending on the clinical manifestations, there are 3 types of skin melanomas: surface-spreading, nodular and lentigo-melanoma. Along with this, the international classification according to the TNM system was adopted in 1997.
- T is a primary tumor, classified depending on the thickness of germination, the presence or absence of ulceration. It is precisely determined only after the treatment.
- N is the state of the regional lymph nodes.
- Nx — there is no reliable data for a correct assessment.
- N0 — there are no signs of lymph node damage.
- N1 — metastases in lymph nodes up to 3 cm in size .
- N2a — metastases more than 3 cm .
- N2b — the presence of metastases in the skin or subcutaneous fat located at a distance of more than 2 cm from the main tumor (transit metastases).
- N2c — the presence of metastases to lymph nodes larger than 3 cm in combination with transit metastases.
- M — distant metastases (extending beyond the regional zone)
- Mx — there is no data to determine the presence of distant metastases.
- M0 — distant metastases are not detected.
- M1a — distant metastases in lymph nodes, skin or subcutaneous fat.
- M1b — the presence of metastases to internal organs.
Melanoma is characterized by a wide variety of clinical picture. Both in terms of the location and size of the tumor, and in terms of its consistency and color. Melanoma can be rounded, polygonal, triangular or have some other shape. The color of the tumor can be black, gray, brown, bluish, pink-purple and gray. Moreover, the color may be uniform over the entire area of the melanoma, or may include a combination of several colors. Depigmented melanomas also occur.
Melanoma can have sizes from a couple of millimeters to 3 cm. Its consistency is usually dense, but it can also be elastic. The surface of the tumor can be unchanged, ulcerated, wet, bleeding when injured or covered with crusts. Characteristic is the absence of a skin pattern on the surface of melanoma. In the vertical phase of its growth, melanoma begins to rise above the surface of the skin, while taking a mushroom-shaped, nodular, bumpy or spherical shape. Cutaneous melanoma metastases manifest as pigmented inclusions, nodules or hyperemia located along the perimeter of the tumor.
The surface-spreading form of melanoma occurs in 60% of cases of the disease. At the beginning of its growth, such a melanoma has the appearance of a small pigment spot with a diameter of up to 5 mm. The spot is colored brown or black and lies in the same plane with the surface of the skin. The horizontal phase of surface-spreading melanoma can stretch for up to 7 years. During the transition to the vertical phase of development, there is a sharp growth of the tumor and its elevation above the skin level.
The nodular form of melanoma in the structure of the disease is about 20%. It is characterized by the shape of a node, polyp or mushroom. The color of the tumor is more often blue-red or black. Due to the fact that nodular melanoma initially rises above the skin level, it was previously believed that it does not have a horizontal phase of development. However, it has now been proven that this is not the case.
Lentigo-melanoma occurs during the malignant transformation of Dubreuil’s melanosis. It accounts for 20% of all melanomas. It has a fairly long period of horizontal growth (10-20 years). In the vertical phase of development, the lesion becomes irregularly shaped with uneven edges and uneven staining.
Through the lymphatic vessels, melanoma metastasizes to the lymph nodes and skin. According to the clinical picture, skin metastases are divided into nodular, satellite, erysipelas and thrombophlebitis-like. Nodular metastases of melanoma are characterized by multiple nodules of various sizes located subcutaneously at different distances from the primary tumor. Satellite metastases are located around the primary melanoma in the form of pigment spots having the same color as the primary focus. The erysipelas-like form of metastasis has the appearance of redness and swelling of the skin around the melanoma focus. With a thrombophlebitis-like form, redness of the skin and expansion of superficially located veins in the skin area around the melanoma are observed, radially painful seals are revealed.
The spread of melanoma tumor cells through the blood vessels leads to the appearance of distant metastases in internal organs: lungs, liver, bones, brain, adrenal glands, kidneys.
The diversity of the clinical picture and the absence of vivid symptoms at the beginning of the disease complicates the timely diagnosis of melanoma. It is possible to suspect the transformation of the nevus into melanoma when its color changes, the appearance of unevenness in staining, smoothing its borders, increasing the size, and the disappearance of the skin pattern on the surface of the nevus. The appearance of redness around the nevus, erosion of its surface, the appearance of cracks, bleeding or unpleasant sensations in the nevus area are also a reason for an urgent consultation with a dermatologist.
When examining the formation, its edges, density, and displacement relative to the surrounding tissues are evaluated. Dermatoscopy of the formation and the surrounding skin is performed. To detect melanoma metastases, other areas of the skin are examined, as well as regional lymph nodes. It is possible to conduct a radioisotope study. The patient takes a radiopreparation on an empty stomach. Then, using radiometry, the accumulation of the isotope in the area of education and on a healthy area of the skin is evaluated.
In the diagnosis of melanoma, a biopsy of the skin formation is categorically not used, since it can cause tumor growth and metastasis. The main diagnostic method is the detection of atypical melanocytes during cytological examination of a smear-imprint taken from the surface of the formation. However, the final diagnosis of melanoma can be made only after histological examination of the removed tumor.
The choice of the melanoma treatment method depends on the phase of its development, the prevalence of the process and the presence of metastasis. If treatment is initiated in the phase of horizontal growth of melanoma, then surgical excision within healthy tissues is sufficient. If deep tumor germination is detected, surgical treatment is combined with alpha-interferon immunochemotherapy to prevent relapse. Metastasis of melanoma to regional lymph nodes is an indication for their removal.
The detection of several melanomas requires the removal of all of them and additional chemotherapy, irradiation of the affected areas of the skin or combination of these methods with immunotherapy. Patients with distant melanoma metastases undergo palliative treatment: excision of large tumor foci that cause the patient severe discomfort. In some cases, it is possible to perform operations to remove metastases from internal organs. Radiation and chemotherapy are also performed.
Prognosis and prevention
Unfortunately, even at the current level of medical development, every third case of melanoma ends in a rapid fatal outcome. About half of the patients fail to prolong their life for more than 5 years.
Prevention of melanoma consists in avoiding the effects of provoking factors and oncological alertness with respect to existing pigment nevi. People with fair skin, especially owners of the I and II phototypes, should avoid excessive insolation and sunburn. It is important to limit the effect of ultraviolet rays on those areas of the skin where the pigment nevi are located. If there are sudden changes in the size, color or consistency of the nevus, it is necessary to consult a dermatologist or oncologist. Timely diagnosis and surgical excision of melanoma-threatening skin formations and often traumatized nevi prevents their transformation into melanoma.