An asymmetrical mole is a spot whose two halves do not look alike. This can be a harmless feature, but it is also one possible warning sign of melanoma, a type of skin cancer. Shape alone cannot tell what a mole is. A new or changing mole, especially with uneven edges or color, should be checked by a healthcare professional.
What does asymmetry in a mole look like?
A mole is asymmetrical when one half looks different from the other half in shape or size. For example, if you imagine a line through the middle of the mole, the two sides may not match. One side might be wider, one edge might extend farther outward, or the overall outline might look uneven.
The American Academy of Dermatology (AAD) identifies asymmetry as the first feature in the ABCDE guide used to recognize possible warning signs of melanoma. However, asymmetry is a feature to pay attention to, not a diagnosis. Some noncancerous moles naturally have irregular shapes, while some melanomas may show only one or two warning signs.
What can an asymmetrical mole mean?
An uneven mole can have several explanations. Its shape may simply be part of its normal appearance, or it may be an atypical mole that looks different from most ordinary moles. In some cases, asymmetry may be associated with melanoma, a type of skin cancer that develops from pigment-producing cells in the skin.
According to Mayo Clinic, an asymmetrical shape, irregular borders, or changes in a mole's color, size, or height can be warning signs that need medical assessment. These features are considered together rather than used individually to determine whether a mole is cancerous.
Could it be a harmless or atypical mole?
Yes. Some ordinary moles do not have perfectly round or balanced outlines. Another possibility is an atypical mole, also called a dysplastic nevus. These moles may be larger than common moles and can have irregular borders, varied colors, or a different surface. An atypical mole is not automatically melanoma, although people with certain patterns of atypical moles may have a higher risk of developing melanoma.
The National Cancer Institute (NCI) explains that common moles are generally noncancerous and that atypical moles can differ from ordinary moles in appearance. A dermatologist can assess an unusual spot and decide whether it needs monitoring or further testing.
What other mole changes matter besides asymmetry?
Shape is only one part of assessing a mole. The edges, color, size, and changes over time also matter. The ABCDE guide can help you recognize features worth discussing with a healthcare professional, although it cannot confirm or rule out skin cancer.
- A — Asymmetry: One half of the mole does not match the other half.
- B — Border: The edges are irregular, notched, scalloped, or poorly defined.
- C — Color: The mole has several colors or uneven shades, such as brown, black, red, pink, or white.
- D — Diameter: The spot is larger than about 6 millimeters, roughly the width of a pencil eraser. However, melanoma can be smaller.
- E — Evolving: The mole changes in size, shape, color, or height, or develops new symptoms.
A mole may also become itchy, tender, crusted, or prone to bleeding. These changes can have causes other than melanoma, but a new or persistent change deserves medical attention. The NCI's guide to melanoma appearance notes that melanoma can resemble an existing mole or appear as a new spot, and that its appearance varies from person to person.
When should an asymmetrical mole be checked?
Arrange a medical appointment if you notice a new or changing asymmetrical mole, especially if it also has uneven borders, multiple colors, or other unusual features. It is also important to get advice about a mole that starts bleeding, becomes crusted, or develops persistent itching or pain. You do not need to wait until several warning signs appear before seeking an assessment.
The UK National Health Service (NHS) recommends seeing a healthcare professional about a mole that changes in size, shape, or color, as well as one that becomes painful, itchy, inflamed, bleeding, or crusted. A new or unusual mark that does not go away after a few weeks should also be assessed.
It is worth paying attention to a mole that looks noticeably different from your other moles, even if it is not large. Some melanomas do not display every feature in the ABCDE guide, so the absence of additional warning signs does not necessarily mean that an unusual spot can be ignored.
How do doctors assess an asymmetrical mole?
A healthcare professional will usually examine the mole and may ask when you first noticed it, whether it has changed, and whether you have experienced symptoms such as itching or bleeding. Your medical history and other relevant skin findings can help guide the assessment. A dermatologist may use a handheld magnifying device called a dermatoscope to examine the skin more closely.
If the mole looks suspicious, the clinician may recommend a biopsy, which involves removing some or all of the spot so that the tissue can be examined under a microscope. The NCI explains that melanoma is diagnosed by checking tissue for cancer cells. Not every asymmetrical mole needs a biopsy; the decision depends on the examination and the level of concern.
Can an asymmetrical mole change naturally with age?
Moles often develop during childhood and adolescence, and some ordinary moles grow as a child grows. According to the NCI, normal moles in children may become evenly larger, whereas uneven changes in size, shape, or other features can warrant closer attention. In adults, a new or evolving mole should be assessed rather than automatically attributed to aging.
People of any skin tone can develop melanoma. Because potentially concerning spots may occur in less noticeable areas, it can be helpful to check the skin across the body, including the scalp, palms, soles, and areas around or beneath the nails. Seek advice about an unusual spot in any location rather than relying only on its color or size.
How can you keep track of an unusual mole?
If you have noticed asymmetry, you can take a clear photograph of the mole in good lighting and record the date. A repeat photograph taken under similar conditions may help you notice changes in its shape, color, or size. A mirror or a trusted person's help can be useful for areas that are difficult to see.
Photographs are useful for tracking appearance, but they cannot establish whether a mole is benign or cancerous. Do not delay a medical appointment to collect more photographs if the mole is new, changing, bleeding, or otherwise concerning. A clinician can advise whether the spot needs examination, monitoring, or further testing.