Melanoma, what causes it?

There are many reasons for the formation of moles, which can be present at birth or acquired later in life. This disease is a developmental malformation. Due to accidental abnormalities in the migration of melanocytes from the neural crest to the epidermis, melanocytes are locally aggregated.

1. What are the causes of moles?

There are many reasons for the formation of moles, which can be present at birth or acquired later in life. Some people are born with it, while many others develop it later in life.

This disease is a developmental malformation. Due to accidental abnormalities in the migration of melanocytes from the neural crest to the epidermis, melanocytes are locally aggregated. Moles can generally be divided into three types: junctional nevus, compound nevus, and intradermal nevus. Among them, junctional nevus and intradermal nevus are very likely to cause malignant melanoma.

The destruction of the ozone layer, computer radiation and other factors have increased the risk of developing moles. The formation of a black mole is itself a type of pigmented mole, which often attracts special attention due to its local blackening, rough and raised skin, and hard short hairs.

Special attention should be paid to moles occurring in parts of the body that are prone to friction or injury, such as the mole growing rapidly and becoming larger, the color becoming lighter or darker and brighter, the short hair on the mole falling off, the area around the mole turning red, with blood streaks faintly visible, and the surface breaking and scabbing or even forming ulcers that do not heal for a long time. Swollen lymph nodes nearby or the appearance of small satellite moles around a large mole indicate that the mole has a tendency to become malignant.

2. Symptoms

1. Common acquired pigmented nevus occurs in almost everyone: in this case, it usually occurs in childhood, mostly after 1-2 years of age, but a few new skin lesions may still appear before the age of 30. When the skin lesions first appear, they are the size of a needle tip to a millet grain, gradually increasing in size to form brown, brown or black macules with a diameter less than 15px. Most of them gradually rise above the skin surface and become flat or hemispherical pigmented papules. The lesions have uniform pigmentation, smooth surface and neat edges. After middle age, the lesions gradually soften, shrink in size, and become lighter in color, until they disappear completely.

2. Congenital moles are present at birth: In this case, the incidence of moles is about 1%. The smaller ones are a few millimeters in diameter, while the larger ones cover most of the body. Those larger than 500px are generally called congenital giant nevi. In addition to varying sizes, congenital nevi also often have various shapes. They can be spots, macules, papules, plaques, nodules, papilloma-like or pedunculated papules. Some have nodules of varying sizes on the basis of large plaques. The edges may be irregular, the surface may not be smooth, the pigmentation may be uneven, and the skin lesions often have coarse hair.

3 Blue nevus Ordinary blue nevus: It often occurs in childhood and is bluish-gray or blue in color. In the early stage, it is a papule, which can develop into a nodule, 2-6mm, hard, round or oval, blue-gray or blue-black, raised above the skin surface, growing very slowly, with clear boundaries, and adhered to the epidermis. It mainly occurs on the dorsum of the hands, dorsum of the feet, extensor side of the forearm and face, is mostly solitary, and is not prone to malignant transformation. Cellular blue nevus is often congenital, appearing as large, solid, clear blue-black nodules or plaques with a smooth surface that may be lobed and have clear boundaries. It often occurs on the back or sacrum and coccyx and may become malignant.

(1) Common blue nevus: It is a gray-blue nodule that occurs over many years and grows slowly. Its diameter is generally ～ 6 mm. It is usually single but may also be multiple. It is more common on the upper limbs or face and this type does not worsen.

(2) Cellular blue nevus: It is a blue or blue-black nodule that is generally large and can reach several centimeters. It is present at birth and is more common on the buttocks and coccyx. This type can become malignant.

(3) Malignant blue nevus: This disease is rare. It can be transformed from a cellular blue nevus and is common on the back of the hands, back, and buttocks. The prognosis is uncertain; most patients can survive long term, but a few die from extensive metastasis.