Moles or nevi can be preset at birth (called congenital nevi) or develop later, and disappear with age. They occur due to proliferation of pigment cells in the skin and are generally harmless. These range in size from a dot to up to an inch in diameter, and can have a flat, smooth or rough surface. Most moles are darker in color than the skin color. Moles that remain unchanged during your lifetime are not a cause for concern.
The common cause for development of moles is exposure to ultraviolet light and therefore occurs more frequently in skin areas exposed to sunlight. A change in hormone levels at adolescence or during pregnancy could also result in appearance of moles. Moles could be caused due to genetic reasons too. In fact, dysplastic nevi is the hereditary occurrence of moles all over the body, some larger than normal sizes. The number of moles in this condition range from 100 onwards.
Moles are cause for concern when they become malignant. This condition is a type of skin cancer called malignant melanoma and can be fatal. If spotted early, these malignant growths can be surgical removed. People born with dysplastic nevi should be careful, and any change in appearance or growth of these moles should be reported to the doctor immediately.
The usual sign of malignancy include change in size or shape or elevation of the mole, if it becomes painful or itchy, changes in color, starts bleeding, or you detect more pigmentation around the affected area. The test for malignancy includes a biopsy in which a portion of the mole is excised and examined for cancerous growth by a dermatologist.
The types of moles include dysplastic, blue and halo naevi. In the first type, moles assume a regular outline and carry an increased risk of malignancy. The second type, halo naevi, is benign and is lighter in appearance. Though the risk of malignancy in these cases is rare, this may develop into a skin disorder called vitiligo. In the third type, moles are very deep seated and may reflect a shade of blue.
To prevent melanoma, increased exposure to sunlight should be avoided, especially at mid day. Also, to avoid sunburn, sunscreen with SPF (sun protection factor) rating of at least 15 should be applied to all exposed areas. Any change in appearance of moles should be checked out immediately. People with a family history of melanoma should be extra careful and need to get themselves checked regularly.