Pigmented nevus is the most common benign tumor containing nevus cells, which is found in everyone, and which kind of nevus is prone to malignant transformation has been the most concerned question. To answer this question, we must first clarify the typology of pigmented nevi, because different types of nevi have different probability of malignant transformation, and this article only introduces common pigmented nevi, which are also the most concerned ones.
I. Common types of pigmented nevi
1.Nevus cell nevus: the most common, including junctional nevus, mixed nevus and intradermal nevus.
They are most common on the face and neck, but also on other parts of the body. Most of them occur in childhood, and the number reaches the maximum at the age of 20-29, with an average of 20-30 nevi per person; then the number of nevi decreases with age, and after the age of 60, there are only 4-6 nevi per person on average.
Junctional nevus: It is a brown-black spot with smooth and hairless surface; pathologically, nevus cells are located at the epidermal-dermal junction, so it is called junctional nevus.
Mixed nevus: the nevus is slightly elevated, with smooth surface and clear boundary; it is formed when part of the nevus cells of the junctional nevus enter the dermis downward, and pathologically there are nevus cells at both the epidermal-dermal junction and the superficial layer of the dermis, so it is called mixed nevus.
Intradermal nevus: It is a hemispherical nevus with more protrusions, and its color becomes brown, sometimes even skin color, and it may have hair. It is formed by the nevus cells entering the dermis completely when the mixed nevus reaches adulthood and is called intradermal nevus.
Indication of malignant change: If a nevus cell nevus suddenly increases in size, ulcerates, bleeds or satellite nevus appears next to the nevus, we should consider the possibility of malignant change and go to a specialist for examination and treatment in time.
2. Dysplastic nevus.
Although it is prone to malignant transformation, especially for those who have melanoma in their families, it is good that it is rare in yellow people. However, this kind of mole is common in Caucasians, so it is advocated abroad that this kind of mole should be removed early. They mostly occur in adolescence or even in adulthood, mostly grow on the chest, back and waist, slightly larger than ordinary moles, usually in larger numbers, smooth or slightly elevated in the center, and may be brown, brown-black or orange-red in color, with uneven shades.
3.Congenital giant nevus.
They are present at birth and are more common on the head, face and back. They are large black patches with rough surface and often have black coarse hairs, like animal skin, also called “animal skin nevus”. As children get older, wrinkles or warty protrusions may appear on the surface. About 10% of such nevi may become malignant, so they should be removed and implanted as early as possible.
4. Small congenital nevus.
It is present at birth, but the size is within 20cm (the size of adult). They appear as irregular-shaped brownish-black spots, slightly elevated with age, with smooth or rough surface and sometimes long black hairs. Small congenital nevi have a 0.1% malignancy rate. Therefore, it is better to remove small congenital moles.
What kind of moles need treatment?
From the above mentioned problem of pigmented moles becoming malignant, first of all, we should clarify whether it is congenital or acquired. Congenital giant moles are most likely to become malignant, followed by congenital small moles, and then moles on the soles of the feet, toes, palms of hands, fingers and under the nails, which are easily stimulated by friction and relatively easy to become malignant, and these should be removed early or closely observed and removed in time when there are changes.
Regardless of whether there is hair on the surface or not, hemispherical prominent moles on the head and face basically will not become malignant and can be treated without treatment except for cosmetic needs.
3. Signs of pigmented nevus malignant transformation (ABCDE)
A. Asymmetry, the shape of two sides of a mole is different;
B. Irregular edge;
C. Uneven color, the color of the same mole varies in shades;
D. Diameter more than 6mm;
E. Raised, i.e. a part of the mole is raised.
These cases should be removed for pathological examination as soon as possible.