Dysplastic nevus is a pigmented neoplasm of the skin that tends to malignancy. Clinically, it looks like a mole of different sizes with bizarre borders, irregularly colored in brown and black tones. Dysplastic nevus has a flat surface or rises slightly above the level of healthy skin in the center. It does not have a typical localization, limitation of the number of spilled elements. The preliminary diagnosis is made on the basis of examination and dermatoscopy; the final one is possible only taking into account the data of histological examination after radical excision of the tumor. The prognosis depends on the timeliness of diagnosis and treatment.
Dysplastic nevus is a non–cancerous tumor that is part of the group of birthmarks that can transform into a malignant neoplasm. The disease has no gender, age differences, is not inherited (only a predisposition to inheritance is transmitted). It occurs in 5% of the white population of the planet. The special significance of melanocytic benign tumors lies in the fact that their individual varieties serve as markers of melanoma when testing patients with precancerous skin, the risk of recurrence of a malignant tumor, helping to identify those who are indicated for preventive therapy.
In modern dermatology, there is a whole school engaged in such experiments, the founders of which were scientists from the University of Pittsburgh (USA, Pennsylvania). The essence of the research is the discovery of two specific proteins – markers of melanoma, the most malignant skin tumor. In the process of studying the effect of interferons on the body of patients, it was stated that the high level of activity of STAT1 and STAT3 proteins was associated with the level of activity of moles predisposed to malignancy, the therapeutic effect of interferon therapy was confirmed by adjusting the level of these proteins with high doses of interferons.
Dysplastic nevus is the result of local migration of melanocytes under the influence of exo– and endogenous causes that are unclear to the end. The cells that produce melanin, which determines the color of the skin, are contained in the epidermis, dermis. The physiological role of melanin is to protect the skin from excess sunlight. Since the entire skin needs such protection, melanin is distributed evenly in the layers of the skin. However, in patients with a hereditary predisposition to nevus formation, transmitted by autosomal dominant type, during the intrauterine development of the fetus or immediately after birth, there is a directed migration of cells overflowing with melanin. Family dysplastic nevi are formed – millimeter formations that become noticeable during the hormonal restructuring of the body, increasing in size to 5 cm.
The occurrence of sporadic moles occurs in a different way. First of all, under the influence of ultraviolet light, which causes a mutation of melanocytes, due to the human papillomavirus, which causes melanocytes to divide at twice the rate. The reason for the growth of melanocytes, their point migration is hormonal restructuring of the body (pregnancy, puberty). Probably, a certain role in the occurrence of dysplastic nevus is played by a decrease in local and general immunity.
Dysplastic nevi are divided into two groups depending on the shape, size, degree of possible malignancy:
1. Sporadic dysplastic nevi – acquired precursors of melanoma:
- A typical form is a neoplasm of different shades of brown, rising above the surface of the skin in the center (“fried eggs”): minimum size (from 1 mm to 1.5 cm), medium size (from 1.5 cm to 10 cm), large size (from 10 to 20 cm), giant size (more than 20 see).
- The form of lentigo is a neoplasm of the skin with a flat surface of brown-brown, black color: medium-sized (up to 10 cm), large (up to 20 cm).
- Keratolytic form is a neoplasm with a bumpy surface of light brown color: medium-sized (up to 10 cm), large (up to 20 cm).
- Erythematous form is a neoplasm in the form of a pinkish birthmark: large (20 cm), giant (more than 20 cm).
2. Familial dysplastic nevi (multiple dysplastic nevi syndrome) is the result of a hereditary predisposition in which all family members, even those who do not have such formations on the skin, are at risk of developing melanoma.
- Sporadic (single), acquired form, increasing the risk of malignancy of the nevus by 7-70 times: dysplastic nevus without malignancy into melanoma (type A); dysplastic nevus with malignancy into melanoma (type C).
- Hereditary-familial form is the result of the transmission to relatives of the possibility of melanocytic dysplasia under the influence of UFOs: dysplastic nevus without malignancy into melanoma (type B); dysplastic nevus with malignancy into melanoma (type D 1); dysplastic nevus with malignancy into melanoma (type D 2) – nevus occurs in 2 or more family members, the risk of melanoma increases 1000 times.
Clinical manifestations occur on unchanged skin. The basis of dysplastic nevus is the accumulation of a large amount of melanin in the upper layers of the epidermis, dermis, usually after hyperinsolation. The pigment spot may be the only one, may be accompanied by a rash of new spots (from one to several hundred). The shape of the dysplastic nevus is always incorrect, the borders have bizarre, fuzzy contours. Since the accumulation of melanocytes on the entire surface of the spot is heterogeneous, the color is correspondingly mottled: where there is little melanin, light brown shades prevail, where there is a lot of dark brown, black. It is believed that the color of the mole characterizes the degree of its possible malignancy: the darker the nevus, the greater the probability of its malignancy.
Dysplastic nevus can have a flat surface, bumpy, rise above the skin only in the central part, where the nodule is located. Dysplastic nevus differs from other “relatives” by its initially large size (up to 1.0 cm), non-standard localization on the chest, buttocks, scalp, the ability to appear throughout a person’s life. There are no subjective symptoms.
The clinical diagnosis, assumed on the basis of a consultation with a dermatologist and the results of a dermatoscopy, must necessarily be confirmed by a biopsy of the cutaneous element. It can be puncture, when a limited area of the nevus is taken with a special needle under local anesthesia, or total – it is carried out for diagnostic and therapeutic purposes, removing the tumor completely under anesthesia. A distinctive histological feature of dysplastic nevus is its ability to chaotic growths in the epidermis and dermis (atypical proliferation of melanocytes).
An alternative method of diagnosis is considered cytological examination of cell scraping or smear-imprint from the surface of the tumor. In difficult cases, immunohistochemistry is connected – the most reliable method of biopsy examination, which allows to identify the phenotype of the tumor. Dysplastic nevus is differentiated with other benign neoplasms, Dubrey’s melanosis, melanoma. Since dysplastic nevus is a transitional form between a benign tumor and malignant melanoma, it is extremely important to know the first signs of its malignancy. Any growth of a dysplastic nevus is a reason for immediate treatment to a dermatologist; itching, the appearance of a pink border on the periphery of the mole, a change in the color of the neoplasm, a seal of healthy skin located next to it, an asymmetric surface of the tumor itself are the first indications of malignancy of the process.
Treatment and prevention
Treatment consists in radical removal of skin neoplasms, depends on the timeliness of treatment, completeness of examination, interpretation of the results by a dermatologist. Before removal, the nevus is examined in the rays of a Wood lamp in order to accurately determine the boundaries of the removed area of the skin, to avoid relapse. If there are single dysplastic nevi on the patient’s body (both new and old), they are removed by a specialist with subsequent follow-up throughout life. Multiple nevi are not subject to radical excision. Patients are prescribed applications of 5% fluorouracil with a preventive control examination every 6 months (especially pregnant women, during hormonal adjustment, taking oral contraceptives). It is possible to prescribe a course of interferon therapy.
There is no specific prevention, you should be careful about staying in the sun. To prevent malignancy, a regular examination by a dermatologist is necessary every 6 months. Early detection of melanoma is a guarantee of life preservation. The prognosis depends on the stage of the process and hereditary predisposition.