Pigmented nevus, also referred to as nevus, nevus or nevus, is a benign tumor of the skin most commonly composed of normal pigmented nevus cells and occasionally seen on the surface of mucous membranes. There are various types of clinical manifestations. Most of them are dark brown or black in color, and there are colorless nevi without color. Such as intradermal nevus, junctional nevus, mixed nevus, etc. There are also giant nevus, blue nevus, juvenile melanoma, etc. Some types can become malignant under certain conditions and deserve attention. Pigmented nevi mostly occur on the face, neck and back, and can be seen in any normal human body. They may be present at birth or may gradually appear in the early years of life. Most grow slowly or persist for many years without change, but spontaneous regression rarely occurs. Surgical and non-surgical treatments are available. The treatment is effective. Pigmented nevi are congenital benign tumors composed of pigmented cells, most of which are benign; in later stages, there are malignant cases. Once a pigmented nevus becomes malignant, its malignancy is extremely high and its metastasis rate is the fastest, and the treatment is not ideal. The disease can be seen in all parts of the skin, with the face and neck, chest and back being the preferred sites. A few occur in the mucous membranes, such as the oral cavity, labia, and lid conjunctiva. Certain pigmented nevi in the area of junctional nevi and those with malignant signs should be removed in time.
Disease classification
Nevus is a kind of benign tumor on the body surface. There are three types of nevi according to pathological classification.
1. Junctional nevus: located at the junction of epidermis and dermis. They are mostly found on the palms of hands, soles of feet, lips of mouth and external genital area. The surface is flat or slightly high, and the size is between 1-2 mm, light brown, brown-black or blue-black. Have the possibility of cancerous transformation, which can occur as melanoma.
2. Intradermal nevus: exists in the dermis. The surface is smooth and clearly delineated. It is larger than 1 mm, with patchy growth, flat or slightly elevated. The color is dark and uniform, light brown, dark brown or inky black. Generally not carcinogenic.
3.Mixed nevus: it is a mixture of the above two kinds of nevi, generally like intradermal nevus, and can become cancerous because it has the components of junctional nevus.
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If a nevus suddenly increases in size within a short period of time and rapidly forms a raised nodule with deepening color, you should be alerted. When the nevus expands to a certain extent, papillary proliferation or rupture occurs, forming a small ulcer (often in the shape of a spitfire), and the surface is prone to bleeding and oozing, or covered with bloody crusts, and black dots, black halos or pigmented nodules often appear around it. At the same time, the patient feels localized itching, burning and painful discomfort. If these changes occur on the body of a nevus, one should immediately seek medical attention, preferably by taking a biopsy for pathological examination to clarify the diagnosis.
Symptoms and signs
Intersecting nevi are light or dark brown patches, papules or nodules, usually small, with a smooth, hairless surface, flat or slightly above the epidermis. There are usually no conscious symptoms. Junctional nevi that protrude from the skin surface are vulnerable to washing, shaving, friction and injury, and as a result, symptoms of malignant transformation may occur: such as slight local itching, burning and pain; rapid increase in the size of the nevus; deepening of color; surface infection, rupture, bleeding, or nevus catching as satellite dots, radiating black lines, or melanin rings in the skin; and enlarged lymph nodes in the drainage area where the nevus is located. Malignant melanoma mostly comes from junctional nevi. It is generally believed that hairy nevi and freckle-like pigmented nevi are all intradermal nevi or compound nevi. These nevi are rarely malignant, and if there is malignant transformation, it is from the junctional nevus part.
Diagnostic basis
1. the location, size, color and shape of the nevus, the presence or absence of hair, hyperplasia or ulceration on the surface.
2.Pay attention to the time of onset, the speed of development, and the mildness of the disease.
3.Pathological section examination to distinguish intradermal nevus, junctional nevus, mixed nevus, verrucous nevus, etc.
Etiology of the disease
1.Intradermal nevus is differentiated from large nevus cells, which are more mature small nevus cells and enter into the dermis and its surrounding connective tissue.
2. Junctional nevus cells are at the junction of epidermis and dermis, in the shape of multiple nesting clusters with clear borders and uniform distribution distances; the upper half within each nest is within the underlying layer of epidermis, while the lower half is within the superficial layer of dermis. These nevus cells are large nevus cells with deeper pigmentation.
3.Composite nevus often has both intradermal nevus and residual junctional nevus in the process of nevus cells entering the dermis, which is a mixed form of the above two types of nevus.
Pathological changes
1. junctional nevus: confined nest of nevus cells located at the junction of true and epidermis
2.Intradermal nevus: cell nests are located in the dermis, in which multinucleated nevus cells can be seen.
3.Composite nevus: cell nests are found at the junction of true and epidermis and the upper part of dermis, and the dermal nevus cells are square-shaped, and the nevus cells at this junction are small and contain little pigment.
Treatment principles of pigmented nevus
Most benign melanocytic nevi do not need to be treated, and the general principle is that if they are not treated, they should be treated completely.
If the nevus occurs in a part that is prone to friction and damage, it is best to remove it surgically. Small lesions can also be treated with ultra-pulsed CO2 laser and/or Q-switched laser. Ordinary CO2 laser, freezing, ultra-high frequency electricity, chemical peeling, etc. is more difficult to master its depth, easy to leave scar or incomplete treatment.
2. surgical excision as far as possible, since malignant changes usually occur after the age of 30, the time of excision can wait until adulthood.
3.Treatment of congenital giant nevus Since the malignancy rate is high and half of the malignant changes occur before the age of 5, they should be removed as early as possible after birth.
4.Surgical treatment should be taken for suspected malignant changes All excised moles should be examined pathologically, and if malignant changes are found, they should be expanded and treated as appropriate.
Treatment measures
No treatment is needed. Attention should be paid to the pigmented nevus in the nail bed, so as not to stimulate it casually and not to apply corrosive drugs indiscriminately, so as not to provoke its malignant change. If the nevus increases rapidly within a short period of time, the color deepens and becomes black, the edge becomes red and irregular, the surface bleeds and breaks, and satellite damage appears around it, it indicates that the nevus has signs of malignant transformation, and should be removed surgically and sent for pathological examination now.
Treatment plan
For larger facial nevi without evidence of malignancy, partial excision can be considered in stages, which is better for appearance and function preservation, but it is not applicable to those with malignant tendency. Total excision with adjacent flap transfer or free skin grafting can also be used. If malignancy is suspected, a shell surgery should be used to excise all biopsies at once; the surgery should be performed outside the boundaries of the nevus and an incision should be made on the normal skin. After excision of moles that must be small, the skin wound edges can be subliminally peeled and then directly pulled together and sutured.
Evaluation of curative effect
1.Cure: the treatment achieves the expected effect, the wound heals and has a good shape.
2.Good: the treatment basically reaches the expected effect and the wound heals better
3.Not healed: the treatment did not achieve the expected effect, the wound healing is poor.
Expert Tips
All people have pigmented nevi. According to statistics, after a careful circumferential examination, normal individuals can have as many as 50 nevi, and generally there are 15-20 nevi on average. Because they are common, they are often disposed of carelessly and casually, and there are many lessons to be learned. The vast majority of pigmented nevi are benign and do not have any effect on physical health. Many people worry that pigmented moles are malignant, and it is not an empty talk. Firstly, some pigmented nevi are easily confused with some skin malignant tumors and often misdiagnosed each other; secondly, individual pigmented nevi do have some relationship with melanoma, so we should pay necessary attention to black pigmented nevi and ask dermatologists to identify them when necessary.
If a pigmented nevus appears in the following conditions, it is a sign that malignancy will occur or has occurred, and should be treated as soon as possible.
1. The lesion grows faster or the area does not change significantly but thickens significantly.
2, color change, color darkening, or especially see a light blue hue appear.
3, Hair loss, debridement or satellite foci appear.
4.The surface is broken, bleeding, and ulcers are formed.
5.Tingling or pain, inflammation and other unexplained symptoms appear.