A halo nevus (also called a Sutton nevus) is a usually benign mole with a round white, pigment-free ring around it. It happens when the immune system targets pigment-producing cells in and around the mole. The mole often gradually fades and may disappear; the white ring can repigment over months to years. It is most common in children and young adults. Dermatology 2-Volume Set, 5e, pp. 1118-1119.

Does it turn into vitiligo?
Not exactly. A halo nevus does not “convert” into vitiligo, but some people with halo nevi also have, or later develop, vitiligo elsewhere on the body.

So, the honest answer is: there is no single reliable percentage for halo nevus progressing to vitiligo. Most typical isolated halo nevi do not necessarily mean a person will develop widespread vitiligo.

Seek a dermatology review if the mole is new after age 40, looks asymmetric or irregular, changes rapidly, bleeds, or if white patches are appearing elsewhere. Typical halo nevi in children and teenagers are usually harmless.