Nodular melanoma is one of the types of melanoma characterized by rapid progression and an unfavorable prognosis. Unlike other types of melanoma, it does not have a horizontal growth phase, it grows vertically from the very beginning, penetrates deeply into the underlying tissues. It is a dark brown, grayish, black or dark blue domed exophytic node, or a polyp on a leg with an easily bleeding surface. Areas of necrosis and ulceration are detected on the surface of the tumor. Nodular melanoma is diagnosed taking into account anamnesis, data from epiluminescent dermatoscopy and blood tests for cancer markers. The treatment is operative.
Nodular melanoma ranks second in frequency after surface-spreading melanoma (with the exception of Japan, where nodular melanomas are 9 times more common than surface-spreading ones). According to various data, it is from 14-15% to 30% of the total number of melanomas. It can develop at any age, the peak incidence occurs at 40-60 years. There is a predominance of male patients. Unlike surface-spreading melanoma, nodular melanoma occurs more often on unchanged skin, and not on the background of a pigmented nevus. It usually affects the scalp, neck or trunk. Due to the absence of a horizontal growth phase, it quickly penetrates into the underlying tissues, gives lymphogenic and distant metastases early. The prognosis for nodular melanoma is less favorable than for other types of melanomas. The probability of a fatal outcome reaches 56%. The treatment is carried out by specialists in the field of oncology and dermatology.
The causes of the occurrence are not precisely established. Experts identify several groups of exogenous and endogenous factors that increase the risk of developing nodular melanoma. The most significant exogenous factor is excessive ultraviolet radiation. In addition, the list of harmful exogenous effects that can provoke the occurrence of nodular melanoma includes permanent mechanical trauma, large doses of ionizing and electromagnetic radiation, as well as prolonged contact with some toxic compounds.
The list of endogenous risk factors for the development of nodular melanoma includes genetic predisposition (the presence of similar tumors in close relatives), belonging to the white race and photosensitivity of types I and II (Scandinavian and Central European phototypes, which are characterized by light skin, red, light brown, light brown or dark brown hair). The researchers point out that the probability of developing nodular melanoma increases with the occurrence of immunodeficiency conditions and during periods of hormonal adjustment. The tumor can form on unchanged skin or transform from benign pigmented formations.
Histological examination of nodular melanoma always determines the deep level of invasion. Neoplasia spreads not only over all layers of the epidermis, but also over the underlying dermis and in some cases sprouts subcutaneous tissue. At the edge of the node, you can see the infiltration of melanocytes. Taking into account the characteristics of atypical cells, several types of nodular melanoma are distinguished: fusiform, epithelioid and non-cellular. There are also mixed variants (for example, a combination of non–cellular and fusiform cell melanoma), including non-pigmented ones.
Symptoms and diagnosis
The development of nodular melanoma on average takes from 6 to 18 months. In the initial stages, unusual sensations are usually absent. With progression, swelling, itching or burning may occur. Nodular melanoma is usually localized on the head, trunk or face and is a plaque rising above the surface of the skin, a node on a wide base or a polyp on a leg. Unlike other types of melanomas, which are characterized by irregular shape and uneven edges, nodular melanoma has a regular spherical or domed shape.
The color of the tumor can vary significantly. Dark brown, dark blue or black neoplasia are more often detected, weakly pigmented (light gray) and non-pigmented nodular melanomas are less common. In appearance, nodes with a small amount of pigment can be similar to telangiectasia. Rather large pigmented tumors often resemble blueberries. Usually neoplasias have a uniform color, sometimes there are “variegated” neoplasms with a predominance of red, beige and black shades.
The surface of nodular melanomas is rough, bleeds easily. Ulceration and necrosis foci may be detected on the surface. Regional metastasis is manifested by an increase in the corresponding lymph nodes. With the appearance of distant metastases, pain and disorders of the functions of the affected organs are observed. The spread of the oncological process is accompanied by increasing general symptoms. The patient feels constant weakness and loses weight. Hyperthermia is observed.
Nodular melanoma is diagnosed taking into account anamnesis data, a blood test for cancer markers and the results of an eluminescent dermatoscopy. When making a diagnosis, an increase in planar dimensions, a change in the shape, shape and color of the pigment formation within a short period of time, unusual sensations (burning, itching, bursting), as well as increased bleeding, peeling and the presence of ulceration on the surface of nodular melanoma are taken into account.
If regional metastasis is suspected, ultrasound of the lymph nodes is prescribed. If necessary, a biopsy is performed. To exclude hematogenic secondary foci, chest x-ray, ultrasound of the abdominal cavity, scintigraphy of skeletal bones and other diagnostic procedures are performed. Differential diagnosis of nodular melanoma is carried out with other types of melanoma, hemangioma, telangiectatic granuloma, blue nevus and pigmented form of basal cell skin cancer. The final diagnosis is established based on the results of histological examination of the removed tumor.
Treatment and prognosis
The tumor is surgically removed, a wide excision of the melanoma is performed together with the surrounding healthy tissues. The distance from the border of nodular melanoma to the edge of resection can vary from 0.5 to 2 cm. A further increase in the volume of intervention is considered inappropriate, since excision of a significant array of surrounding tissues does not prevent further progression of the oncological process. The removed nodular melanoma is sent for urgent histological examination, which allows confirming the preliminary diagnosis and assessing the radicality of the operation. When malignant cells are detected in the resection zone, the affected tissues are additionally excised.
The tactics of treatment of regional and hematogenous metastases of nodular melanoma depends on the prevalence of the oncological process. In case of regional metastases, total lymphadenectomy is performed in the affected anatomical zone. When determining the treatment plan for patients with hematogenous metastases of nodular melanoma, the number of foci (single, multiple) and the effect of metastases of some localizations on the duration and quality of life (for example, when located in the brain) are taken into account.
Single distant metastases of nodular melanoma and secondary tumors that threaten to shorten the term and worsen the quality of life of the patient, if possible, are surgically removed. In some cases, combination therapy is prescribed for local and widespread processes, which may include surgery, chemotherapy, radiation treatment and immunochemotherapy. In inoperable nodular melanomas, radiotherapy or chemotherapy drugs are used. After radical removal of neoplasia, patients are examined every 3 months for 2 years, and then every six months.
Nodular melanoma is the most unfavorable type of melanoma. The thickness of the neoplasm is indicated as one of the main prognostic factors. Nodular melanomas with a thickness of less than 1.5 mm are considered as prognostically favorable, 1.5-3.5 mm – as doubtful, more than 3.5 mm – as prognostically unfavorable. Due to the primary vertical growth, nodular melanoma penetrates into the underlying tissues very early, therefore, at the time of diagnosis, a significant number of neoplasias are already questionable or prognostically unfavorable. Mortality in nodular melanoma is 56%.