What is a halo mole?
A halo mole (or halo naevus) is a mole with a white ring, or halo, around it. It is sometimes known as Sutton naevus or leukoderma acquisitum centrifugum.
Who gets halo moles?
Halo moles are not uncommon. They are usually seen in healthy children or young adults of either sex. However, they can occur at an older age too.
In some older adults, halo moles are associated with a type of skin cancer, melanoma.
What do halo moles look like?
Halo moles are most often found on the trunk, but may arise on any part of the body.
There are four stages of a halo naevus. It may take several years to complete the cycle. They are often multiple, and the naevi can be at different stages.
- Stage 1: A rim of pale skin surrounds a mole
- Stage 2: The mole may become pinker or less pigmented, and fades away
- Stage 3: A circular or oval area of depigmentation persists
- Stage 4: The affected skin gradually returns to its normal colour
Why do halo naevi arise?
For reasons which are unknown, the body selects a particular mole or moles for destruction. This is presumably because the mole is recognised as being abnormal in some way. It is considered an autoimmune process.
The mole in the centre of a halo is rarely malignant (cancerous) although all halo moles need to be examined carefully by an appropriate medical practitioner. A malignant mole is called a melanoma, and these may sometimes develop white halos around them as well.
Sometimes halo moles are triggered by sunburn which damages the mole and causes it to be recognised by the body as foreign.
A circulating antibody and special white cells (T cells) attack the pigment cells in the mole. This causes the central mole to fade from dark brown to light brown to pink, eventually disappearing completely. Some of the reaction affects the normal skin around the mole, which also has pigment cells in it, causing the white halo. This is usually about 0.5 to 1.0 cm wide, usually on the trunk. They are less common on the head, and are rare on the limbs. They develop at intervals round one or several moles but not all.
What investigations should be done?
If you have a halo mole, get your dermatologist or doctor to check it. A full skin examination should be performed, as rarely, halo moles can be triggered by the presence of a malignant melanoma elsewhere on the skin. Halos can be seen as part of a more generalised pigment loss, vitiligo, or in melanoma.
Occasionally, excision of the mole is recommended to make sure it is benign. Surgery is not usually necessary, particularly in children or in patients with multiple halo naevi.
Treatment of halo mole
Apart from an explanation, no treatment is normally required. However sunscreen should be applied to all the skin during summer to prevent sunburn. The white skin of a halo naevus will burn particularly easily in the sun because it is missing protective melanin pigment.