Melanocyte nevus, melanocytic nevus diagram

Melanocytic nevus

Melanin nevus

Melanocytic nevi is produced by a group of benign melanocytes gathered at the junction of epidermis and dermis. Melanocytic nevi may be distributed in the lower reticular diemis and between the connective tissue bundles. , Other accessory organs surrounding the skin such as sweat glands, hair follicles, blood vessels, nerves, etc., occasionally extend to subcutaneous fat.

Its appearance may look flat, raised, warty, granular, or other shapes, and its color may be brown, black, or blue. There are two types of melanocytic nevi: congenital and acquired.

Most congenital moles are present at birth or during the newborn period, while acquired moles may grow up after six months of age and into old age.

Acquired moles are usually 0.1 to 0.6 centimeters in size, and can be divided into three types pathologically: junctional moles (nevi cells are limited to the junction of the epidermis and dermis, belonging to intra-epidermal moles), compound moles (nevi The cells are not only distributed in the epidermis layer, but down into the dermis layer), intradermal moles (nevi cells are completely located in the dermis layer). The clinical appearance of moles is also related to their pathological classification. Conjunctive moles show brown to black flat spots that do not protrude on the skin surface. Compound moles usually show brown protruding papules or nodules. Intradermal moles are larger and more protruding. Nodules that are light brown or flesh-colored are what most people call "meat moles."

Congenital melanocytic nevi can be found in 1%~2% of newborns, but the incidence of huge congenital melanocytic nevi is less than one in 20,000 (foreign statistics). Clinically, it can be divided into three types according to its size:

Small melanocytic nevi: smaller than two centimeters in size, preferentially distributed on the lower body, upper back, shoulders, chest and proximal limbs.

Intermediate melanocytic nevus: The size is between 2 and 20 cm.

Huge melanocytic mole: The size is greater than 20 cm, and the distribution is mainly on the back half of the torso. There are also some people who are not on the head or limbs, and may cover large areas of the body. It is usually dark and slightly covered with hair, and there are satellite-like lesions scattered outside the main body.

Most congenital giant melanocytic nevi are benign, but congenital giant melanocytic nevi are usually more complicated than acquired giant melanocytic nevi. According to its growth pattern, it can be divided into three types:

Compound or intradermal nervus (compound or intradermal nervus): It occurs most often.

Neural nervus: Neural tube or neuroma can appear in the structure, which looks a lot like neurofibromas.

Blue mole (blue nervus): the least common.

Melanoma must be distinguished clinically from melanoma. Melanoma has the highest mortality rate among skin cancers, accounting for about two-thirds of all skin cancer deaths. According to Western statistics, about 20-50% of melanomas are related to moles. Therefore, it is very important to distinguish whether a mole is associated with melanoma. Generally distinguished according to ABCDE, A is Asymmetry asymmetry, that is, the lesion is asymmetry up and down, left and right (imagine that the lesion can be folded up and down or left and right like origami); B is Border Irregularity with irregular edges, that is, the edges do not form a circular arc. , And there is a jagged gap; C is Color Variability, the color is not uniform, some parts are deep pigmented, and some parts are lightly pigmented; D is Diameter> 6mm, and the diameter of the lesion is greater than 0.6 cm; E is Elevation or Enlargement, which is The surface becomes protruding or the size of the lesion increases. For any lesions that are suspected of being medically malignant, biopsy and pathological tests must be accepted. Fortunately, among Asians, the incidence of melanoma combined with moles is much less than that of Caucasians.

Causes and prevention

Ultraviolet rays are a major cause of the formation of melanin. In daily life, the formation of melanin can be well inhibited by applying sunscreen while performing whitening care. Because during whitening care, the melanin that has been produced can be slowly eliminated, and sunscreen can help the skin to inhibit the production of new melanin. Good sunscreen products can protect the skin's basal layer and dermis from ultraviolet rays without stimulating the activity of tyrosinase, that is, it can inhibit the production of melanin. The slow alternation of old and new keratin is also one of the reasons for the formation of melanin. Therefore, regular exfoliation of keratin is very helpful for whitening skin. The acidic substances added in many whitening products now help peel off aging keratin and remove melanin. .

The skin tone can also be improved through diet. For example, drink plenty of water, eat more vegetables and fruits, strengthen the intake of antioxidant foods, and eat more foods rich in vitamin C. Chemical experiments have proved that most of the series of reactions in the formation of melanin are oxidation reactions, but when vitamin C is added, the formation of melanin can be blocked. Therefore, eat more foods rich in vitamin C, such as wild dates, fresh dates, tomatoes, pears, oranges, and fresh green leafy vegetables.

Melanoma is a benign tumor in medicine and generally does not require treatment. For patients who want to remove melanoma, it is best to choose a skin specialist to treat it more securely. Commonly used treatment methods include surgical resection, laser treatment, and electric wave knife resection.

What diseases are easy to be confused with melanin nevus?

1. Benign junctional moles

The microscopic findings are benign nevus cells and no heterogeneous cells, only growing in the dermis, and the inflammatory response is not obvious

2. Juvenile melanoma

On the child’s face, there is a slow-growing round nodule. The cells are seen under the microscope. The cells are pleomorphic. Mitogenoma cells do not infiltrate the epidermis and the tumor surface does not form ulcers.

3. Cellular blue nevus

Occurs in the gluteal coccyx, sacral and lumbar areas, with light blue nodules. The surface is smooth and irregular. Dark black cells with dendritic processes can be seen under the microscope. Large prismatic cells are assembled into cell islands. Malignant transformation should be considered when mitotic phases or necrotic areas are present. may

4. Basal cell carcinoma

It is a malignant tumor of epithelial cells that infiltrates from the basal layer of the epidermis to the deep part of the cancer nest. The surrounding cells are columnar or cuboidal. The cancer cells are stained deeply and irregularly. The cancer cells may contain melanin.

5. Sclerosing hemangioma

Hyperkeratosis of the epidermis The milky proliferation and expansion of the capillaries in the dermis are often surrounded by downwardly extending epidermal protrusions, which look like intra-epidermal hematomas.

6. Aged moles

It can be seen in the elderly with wart-like moles. Hyperkeratosis of the epidermis is partially thickened or atrophied. The spinous layer is thick and the base layer is intact. There may also be increased pigmentation of the dermal papilla. The appearance is papilloma-like hyperplasia.

7. Seborrheic keratosis

The lesion is also papilloma-like hyperplasia. The subcutaneous boundary is clear. Incomplete keratinization. The granular layer first thickens and then becomes thinner or even disappears. There may be a small amount or more of melanin in the hyperplastic epidermal cells

8. Hematoma under the nail bed

There are many corresponding traumatic history. The blood cells are dry under the microscope may have epithelial fibroblast proliferation

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