How are moles formed?
Differentiate from diseases with pigmentary lesions, such as senile black spots: it is more common in exposed parts of middle-aged and elderly people, such as cheeks, neck, back of hand, forearm, etc., and it is mostly brown, small round, oval or irregularly smooth or slightly higher than the skin surface. Histological examination showed that normal melanocytes increased without malignant transformation.
Often appear after the age of two. It can occur in the skin and mucous membranes of any part of the body. The lesions are flat or slightly raised maculopapules or maculopapules, and they can also be hemispherical, papilloma-like or pedicled, with or without hair, and the number can be single, several to dozens. Because of the different types and contents of pigments in nevus cells, lesions can be brown, blue-black or black, and non-pigmented lesions are mostly skin color. According to the different positions of nevus cells in the skin, it can be divided into borderline nevus, mixed nevus and intradermal nevus. The flat lesions suggest borderline nevus, and the slightly higher lesions are mostly mixed nevus, while papilloma-like lesions and almost all hemispherical and pedicled lesions are intradermal nevus. The disease progresses slowly, and most of them have no conscious symptoms.
Nevus with atypical appearance may become malignant, such as dark nevus, uneven pigment, uneven or irregular edge, unclear boundary, asymmetric left and right, and statistically larger than 5 mm in diameter. Nevus growing in nail groove and nails, limbs, oral mucosa, conjunctiva, vagina and foreskin are more likely to become malignant melanoma than those growing in other places.