Understanding Halo Moles
A mole is a common skin growth that appears as a small, dark spot. While most moles are uniform in color and shape, a specific type known as a halo mole presents with a distinct appearance.
Halo moles are easily recognizable by a central mole surrounded by a ring of depigmented, or lighter, skin. The central mole can vary in color, appearing brown, black, or even pink. This lighter ring of skin typically forms a circular border around the mole.
These moles are also referred to by medical terms such as Sutton’s nevi or leukoderma acquisitum centrifugum. They can appear anywhere on the body, though they are frequently observed on the trunk, head, and neck. The central mole is typically benign, and its surrounding white halo is an identifying feature.
Are Halo Moles a Concern?
Halo moles are generally considered non-cancerous and are a common occurrence, particularly in children and young adults. The distinctive white ring around the mole is a result of the body’s immune system. The immune system identifies the mole cells as foreign and mounts a response to eliminate them.
This immune process, often involving lymphocytes, attacks the pigment-producing cells within the mole and the surrounding skin. The immune response is typically self-limiting, meaning it resolves on its own over time. As a result, the central mole often fades and may eventually disappear completely.
While halo moles are generally benign, very rare associations exist with conditions like vitiligo or, in extremely rare cases, melanoma.
When to Consult a Doctor
While halo moles are generally benign, certain changes or features warrant a medical evaluation. It is important to consult a doctor if the central mole within the halo changes significantly in its appearance. This includes alterations in size, shape, color, or texture.
Concerning signs include the mole becoming asymmetrical or developing irregular borders. Uneven coloration within the mole, or a diameter larger than 6 millimeters, are also concerning signs. Additionally, if the mole becomes itchy, painful, or starts to bleed, consult a doctor.
The appearance of a halo around a mole that looks atypical or suspicious, even before the halo forms, is another reason for concern. While halo moles are common in younger individuals, the sudden appearance of multiple halo moles in adulthood might also warrant further investigation by a doctor. A dermatologist can perform a visual inspection, use a dermoscope, and may recommend a biopsy if needed to assess the mole.
Why Do Halo Moles Form?
The formation of a halo mole is primarily attributed to a specific immune system reaction. The body’s immune cells, particularly lymphocytes, recognize the melanocytes within the mole as targets. Melanocytes are the cells responsible for producing pigment in the skin.
These lymphocytes then launch an attack not only on the melanocytes within the mole but also on the pigment cells in the surrounding skin. This targeted destruction of melanocytes leads to the depigmentation that creates the characteristic white halo. The process is often spontaneous and represents a natural immune response to the mole.
The exact triggers for this immune response are not fully understood. It is not typically linked to external factors like sun exposure in the same way that other types of moles or skin changes might be.