Superficially spreading melanoma is the most common type of melanoma. It is usually diagnosed at a young and middle age, more often affects the skin of the trunk and lower extremities. In the initial stages, it is an unevenly pigmented spot with clear borders, slightly raised above the skin level. Subsequently, the tumor increases, becomes lumpy and ulcerates. Areas of necrosis form on the surface. The tumor forms satellites and gives metastases. It is diagnosed taking into account the data of dermatoscopy, analysis for cancer markers and the results of postoperative biopsy. Treatment – surgery, radiotherapy.
General information
Surface spreading melanoma accounts for about 70% of the total structure of melanomas. It usually develops against the background of a pigmented nevus. The average age of onset of the disease is 30-50 years. In 98% of cases, it affects persons belonging to the white race. There is a predominance of female patients. In women, the neoplasm is more often detected in the lower extremities, in men – in the back area. In representatives of the Negroid race of both sexes, superficially spreading melanoma usually develops in the area of the soles.
The growth phases are similar to lentigo-melanoma and acral-lentingiose melanoma. Initially, the tumor grows horizontally on the surface of the skin (the phase of horizontal or radial growth). At this stage, the disease proceeds relatively favorably, the formation of secondary foci is uncharacteristic. Then comes the phase of vertical growth, during which the melanoma penetrates into the underlying tissues and quickly metastases. During the transition to the vertical growth phase, the forecast deteriorates significantly. The treatment is carried out by specialists in the field of oncology and dermatology.
Causes
The causes of the development are not exactly clarified. Neoplasia is formed against the background of benign pigment formations-precursors – dysplastic nevus or congenital non-cellular nevus. Approximately 10% of patients have a hereditary predisposition (the presence of melanomas in first- and second-line relatives). Superficially spreading melanoma is more often affected by blue-eyed blondes with light skin. There is a connection with excessive insolation, a particularly significant role is played by constant prolonged exposure to the sun (a steady desire to achieve a noticeable tan) and repeated sunburn, including those separated by significant time intervals.
The most important distinguishing histological features of surface-spreading melanoma are the type and patterns of distribution of atypical cells in the horizontal growth phase. Neoplasia cells are large, cytoplasm is abundant, pigment granules are visible in it. The nuclei are also large, with an uneven membrane and eosinophilic nucleoli. Cells are detected in all layers of the epidermis up to the papillary layer of the dermis. Lymphocytic infiltration is detected in the dermis.
In the phase of vertical growth, the histological picture of surface-spreading melanoma undergoes certain changes. Atypical melanocytes first infiltrate the papillary and reticular layers of the dermis, and then penetrate into the underlying tissues. In their appearance, the cells of the neoplasm are close to epithelioid. The amount of pigment in the cytoplasm decreases. Infiltration becomes less pronounced and is detected along the periphery of the neoplasm.
Symptoms
In the early stages, melanoma is a brownish spot of uneven color with black and pinkish-gray inclusions. The predominant color of the spot is determined by the zones of clusters of atypical melanocytes. Cells in the stratum corneum stain neoplasia black, cells at the level of the basement membrane – brown. The spot rises slightly above the skin level. The edges of the spot are clear, smooth, irregular in shape. The rim of hyperemia is visible along the periphery.
The duration of the horizontal growth phase of surface-spreading melanoma ranges from several months to several years. During this time, the tumor becomes denser, its surface turns black and acquires a glossy sheen. In some patients, neoplasms with a depigmented center and dense black edges are detected. The flat spot gradually turns into a more convex node. The skin in the area of the node is thinning, the neoplasm bleeds easily. Ulceration and necrosis foci appear on the surface of melanoma.
Satellites appear around neoplasia, indicating the local spread of the oncological process. Lymphogenic metastasis of surface-spreading melanoma is accompanied by an increase in regional lymph nodes. Hematogenic foci may appear in the lungs, liver, bones, brain, kidneys and adrenal glands. With distant metastases, disorders from the affected organs may be detected. In the final stages, marked weakness, fever and a significant decrease in body weight are noted.
Diagnostics
Diagnosis is based on anamnesis, the result of a blood test for cancer markers and visual signs of surface-spreading melanoma detected during dermatoscopy. The asymmetry of the spot, uneven edges, heterogeneity of color and a diameter of more than 6 mm testify in favor of melanoma. At the same time, it is taken into account that none of the listed characteristics is an absolute confirmation of the malignancy of the process. When making a preliminary diagnosis, the elevation of the neoplasm above the surface of the skin, the change in size, shape and color of the spot over the past few months or years are also taken into account.
Dermatooncologists do not perform a preoperative biopsy for superficially spreading melanomas due to an increase in the probability of metastasis. Differential diagnosis is carried out with other types of melanoma, Paget’s disease and dysplastic nevus. The final diagnosis is made on the basis of histological examination of the removed tumor. To detect lymphogenic metastases, ultrasound and biopsy of lymph nodes are performed. The presence of hematogenous metastases is confirmed by the data of scintigraphy of skeletal bones, chest X-ray, ultrasound of the abdominal cavity and other studies.
Treatment and prognosis
The treatment is operative. Neoplasia is excised together with 0.5-2 cm of surrounding healthy tissues. An urgent histological examination is carried out to identify malignant cells along the edge of the incision. If there are signs of the spread of melanoma to the incision zone, the scope of the operation is expanded. In some cases, combination therapy is also used, which is a combination of short-focus radiotherapy and surgical intervention. With superficially spreading melanoma with lymph node damage, a total regional lymphadenectomy is performed. In the presence of single distant metastases and metastases that pose an immediate danger to the patient’s life, surgical removal of secondary foci is carried out.
If radical treatment is not possible, palliative therapy is prescribed. For example, in case of multiple bone metastasis, systemic radionuclide therapy is performed, which, despite the low sensitivity of surface-spreading melanoma to this type of therapy, can significantly reduce the intensity of pain syndrome. Palliative treatment can include both radiation therapy and chemotherapy, which in some cases allows to reduce the size of secondary foci, increase the duration and improve the quality of life of patients.
The prognosis depends on the growth phase, thickness and prevalence of surface-spreading melanoma. The average mortality rate for this disease is 31%. The probability of lymphogenic metastasis ranges from 5% in the horizontal growth phase to 35-75% in the vertical growth phase. The thickness of the neoplasm less than 1.5 mm is considered prognostically favorable. With a thickness of 1.5-3.5 mm neoplasia, the prognosis is assessed as doubtful, with a thickness of more than 3.5 mm – as poor. Prevention of relapses involves quarterly examinations, palpation of lymph nodes and instrumental studies (radiography, ultrasound, MRI) in the first 2 years after surgical removal of a superficially spreading melanoma. In the next 3 years, these events are held every 6 months.