Halo nevus is a mole that is surrounded by a pale ring or 'halo'. It is generally noticed in the summer, when surrounding skin tans, and usually occurs on the chest, but can be anywhere. There may be one or, more typically, several. Onset is usually in teenagers and young adults. It typically follows a pattern of appearing at first as a dark mole surrounded by a halo before the nevus fades and disappears. A single halo-nevus-like lesion appearing in an older adult may be a melanoma.