Lentigo maligna melanoma is a type of melanoma characterized by a long course. It is a spot of irregular shape. It occurs more often in open areas of the body, less often affects the skin of the back and lower extremities. Lentigo melanoma has a long phase of radial growth, sometimes lasting one to two decades. Subsequently, it goes into a phase of vertical growth, which lasts from several months to several years. The risk of metastasis is lower than in other types of melanoma. The diagnosis is made on the basis of dermatoscopy data, blood tests for cancer markers and postoperative histological examination. The treatment is operative.
General information
Lentigo maligna melanoma is the rarest of the four main types of melanoma: surface-spreading melanoma, acral-lentinginous, nodular and lentigo maligna melanoma. It makes up from 5 to 10% of the total number of melanomas. It is characterized by the most favorable current. The total duration of the disease from the appearance of the first signs of malignancy to the germination of the underlying tissues and the formation of metastases ranges from 2 to 20 years. At the same time, in the vertical growth phase, lentigo maligna melanoma is capable of rapid metastasis, which causes the death of the patient.
In 85% of cases, the tumor affects open areas of the body: the face, ears, scalp, neck and the back of the hands. 15% are accounted for by lentigo maligna melanomas of other localizations (mainly of the back and lower extremities). Women suffer twice as often as men, while their neoplasms occur later and are less malignant. Usually, lentigo melanoma is diagnosed after 40 years. The average age at the time of diagnosis in men is 50-60 years, in women – 60-70 years. The treatment is carried out by specialists in the field of oncology and dermatology.
Causes
This form of melanoma occurs against the background of a precancerous skin disease – Dubreuil’s melanosis (in some sources – Dubreuil), which is characterized by the presence of pigment spots of different colors, sizes and shapes resembling large freckles. Risk factors for the development of Dubray melanosis, in turn, are considered excessive insolation, permanent traumatization of the skin and drying of the skin under the influence of adverse meteorological factors. Dubrey’s melanosis is more often affected by light-skinned blondes. Thus, lentigo maligna melanoma occurs under the influence of the same predisposing factors as other types of melanomas, while the development of a malignant neoplasm is preceded by a change in the skin, characteristic of this type of oncological skin lesion.
Macroscopically, lentigo maligna melanoma is an irregularly colored spot of irregular shape. The diameter of the spot varies from a few millimeters to 2-5 cm, individual cases of melanomas of about 20 cm in size are described. Microscopic examination of lentigo maligna melanoma in the initial stages determines the proliferation of large atypical melanocytes with abundant cytoplasm and hyperchromic nuclei. With Dubrey’s melanosis, melanocytes do not spread to the stratum corneum of the skin, with degeneration into lentigo maligna melanoma, infiltration of all layers of the epidermis is observed.
Areas of malignant degeneration may alternate with areas without signs of malignancy. In the presence of hair follicles in the affected area, chains are identified that “encircle” the outer parts of these follicles. During the transition of lentigo maligna melanoma to the phase of vertical growth, the zones of unchanged cells disappear, atypical cells penetrate beyond the epidermis and form clusters of small size (“pseudoacontic abscesses”). Examination of the dermis reveals an increase in the diameter of capillaries, lymphocytic infiltration and hyperelastosis of the stroma.
There are also lentigo maligna melanomas, which are brownish lumpy tumors without signs of background changes characteristic of melanosis. With dermatoscopy of such neoplasms, the disappearance of the skin pattern is determined. Microscopic examination of lentigo maligna melanoma indicates the presence of reactive overgrowth and thickening of the epidermis. Atypical neoplasm cells are grouped into strands and bulky clusters, more often located in the lower part of the epidermis. Separate structures of atypical melanocytes localized in the upper part of the epidermis are also revealed.
Symptoms
In the early stages, lentigo maligna melanoma has a rather pale color and looks like a large freckle or brownish spot on the skin. With the progression of the lentigo maligna melanoma process, it begins to stand out more clearly against the background of the surrounding unchanged skin. The size of neoplasia increases, while the growth rate can vary significantly – from a few millimeters to several centimeters during the year.
The color of lentigo melanoma can vary from rich brown to pink, yellowish, red or white. Uneven coloring and irregular clear contours are characteristic. Sometimes large lentigo maligna melanomas, due to the heterogeneity of color and complexity of contours, resemble a geographical map. Often there are tumors that look like a bright blot on the background of paler “divorces”. The boundaries of lentigo maligna melanoma are clear, the surface is smooth. The tumor does not rise above the unchanged skin.
During the transition to the phase of vertical growth, the boundaries of the neoplasm become less clear, begin to resemble a zigzag or wavy line. The spot rises above the surface of the skin. Nodules, peeling areas, cracks, crusts and ulceration foci appear on the surface of the spot. The color of lentigo melanoma can change to bluish, purple or black. Patients note the appearance of itching in the area of neoplasia. After the transition to the vertical growth phase, metastasis to lymph nodes and distant organs is possible. With the spread of the tumor process, common symptoms of oncological damage appear: weight loss, weakness, increased fatigue and hyperthermia.
Diagnostics
Lentigo maligna melanoma is diagnosed by a dermatologist on the basis of complaints, medical history, results of external examination and additional studies. The examination plan includes a dermatoscopy and a blood test for cancer markers. When examined with a dermatoscope, the boundaries and structure of the neoplasm are evaluated. If vertical growth of lentigo maligna melanoma is suspected, a biopsy of regional lymph nodes and other studies aimed at detecting lymphogenic and hematogenic metastases are performed.
A biopsy of the primary focus at the diagnostic stage is not indicated due to the danger of the spread of malignant cells. According to WHO standards, excision biopsy of unchanged skin at a distance of 2 mm–1 cm from neoplasia is allowed. Histological examination to confirm the diagnosis of lentigo maligna melanoma is performed after surgical excision of the tumor.
Treatment and prognosis
Treatment of this pathology is carried out according to the same principles as for other types of melanomas. The main method of treatment of lentigo maligna melanoma is surgical intervention. The neoplasm is widely excised with the capture of the surrounding unchanged tissues. The amount of indentation from the edge of the lentigo melanoma to the incision site is determined depending on the stage of the process and can range from 0.5 to 2 cm. A further increase in the indentation is not recommended as not providing an increase in the effectiveness of treatment.
In case of lentigo maligna melanoma with lymphogenic metastases, regional lymphadenectomy with removal of all deep and superficial nodes of this anatomical area is recommended. In the presence of distant metastases, the tactics of treatment of lentigo maligna melanoma is determined individually, depending on the localization of secondary foci and the prevalence of the oncological process. Single resectable metastases and metastases that pose an immediate threat to the patient’s life are surgically removed.
The possibilities of chemotherapy and radiation therapy are limited due to the low sensitivity of lentigo maligna melanoma to the listed effects. The use of these methods of treatment is advisable in the presence of multiple metastases. Monotherapy or combination therapy is possible. The prognosis is determined by the phase of the oncological process. With radial (surface) growth, a 100% five-year survival rate is observed. In the vertical growth phase, the prognosis for lentigo melanoma worsens significantly, only 15% of patients manage to live up to five years from the moment of surgery.