A young adult presents with an asymptomatic but recently changing mole on his arm.
Key point: The white halo surrounding a nevus is pathognomonic for a halo nevus. This likely represents an attack of the body’s own immune system on the melanin-producing cells comprising the lesion (nevus cells).
Treatment: The entire nevus will probably disappear, leaving a white macule which may remain as is or re-pigment over time. No treatment is needed. Excision will probably leave a worse cosmetic outcome than the course of nature.
Note: It was previously thought that the appearance of a halo nevus meant that the original lesion had undergone malignant transformation or that the patient was harboring an occult melanoma elsewhere. However, in the absence of clear symptoms, this is considered a benign phenomenon, and costly melanoma “hunts” are no longer recommended.