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You have a mole removed and the pathology report tells you that the mole is fine but ‘could have turned into a melanoma.’ This really doesn’t tell the whole story and can be a little frightening if you don’t understand.
An atypical mole:
- Is not a ‘normal-looking mole.’
- Is not a melanoma
- Causes concern for you
- May causes concern for your doctor
An atypical mole may be larger, darker, or have a greater range of colours than a simple mole. The border may also be irregular.
In other words, an atypical mole looks very similar to a melanoma.
A dermoscopy or examination of the skin using a dermoscope is very helpful in these cases. However, your doctor may still not be able to tell if a lesion is a melanoma or an atypical mole (dysplastic nevus) without a biopsy. Unfortunately, this kind of confusion can’t be avoided because regular screenings are key to detecting melanoma as early as possible.
The term atypical mole is used by doctors during a skin check, whilst the term dysplastic mole is used by pathologists.
Even a pathologist may have difficulty telling a melanoma from a dysplastic nevus. And just to be sure, they will often treat a ‘Severely dysplastic nevus’ as a melanoma.
The Mole That ‘Was Turning’
Let’s get back to that story. So, your skin doctor or Dermatologist phones you after a skin biopsy. The pathology report identifies a dysplastic nevus and informs you that it ‘might have turned into a melanoma.’
Scary, right? However, the chances that a ‘dysplastic nevus’ will turn into a melanoma are very small. And your doctor wasn’t looking for atypical moles when they recommended the biopsy, they were looking for melanoma. Which they didn’t find. What they found was an unusual mole that falls under one of two classifications.
These classifications were changed in 2018 by the World Health Organisation:
- ‘mildly dysplastic’ moles are now called ‘low grade’
- ‘severely dysplastic’ moles are now ‘high grade.’
- ‘Moderately dysplastic’ is no longer used and most moles in this category are now reclassified as low grade
These new classifications help to overcome any disagreements about the appearance of atypical moles. The appearance of moles can be very subjective and it’s often difficult to identify when a mole is a problem and should be removed. With the new classifications, high-grade moles are often indistinguishable from melanoma and should be re-excised with wider margins.
There is no evidence that dysplastic naevi are, in fact, common precursors of melanoma*
What are the clinical features?
Here are some of the features of an atypical mole:
- Size: 5mm or more in diameter
- Color: variable with different shades of brown, black or red
- Edge: Irregular
- Surface: might be irregular or cobble-stoned
- There tend to be a lot more moles in general
When you have a troubling mole, your doctor will compare the above features with key melanoma features to find the best match.
Atypical Moles by type
The golden rule is that ‘mildly’ or ‘moderately’ dysplastic moles, (also called ‘low grade’) are basically ‘all good.’
A ‘severely’ dysplastic nevus is as close as you can get to a melanoma without being a melanoma, and will need further treatment.
‘Moderately Dysplastic’ – most of these would now be called low grade atypical moles.
Atypical Moles – multiple
The Danger of Atypical Moles
Atypical Moles and Melanoma Risk
Atypical moles are a risk factor for developing melanoma. Melanoma is around ten times more common in people who have more than five Atypical moles.
‘Normal-looking moles’ are also a risk factor for melanoma, but you’d have to have a lot more normal moles to increase your risk. If you have more than 100 simple moles, then your risk of melanoma is around seven times greater than someone with an average number of moles (around 30).
An additional concern is that a mole that looks atypical may actually be a melanoma. Your doctor doesn’t want to make this mistake, which is why you may have to get atypical moles biopsied. A careful visual exam will reduce but not eliminate the need to biopsy an atypical mole.
Moles and Melanoma Thickness
There is also an association between the number of atypical moles a person has and the thickness of melanoma. This was found in a study of 566 people with atypical moles published in 2016.
The authors of the study state that ‘Younger patients should be educated on the increased risk of thicker melanomas that is associated with having more atypical nevi (moles).’ For this group, more frequent skin checks may be necessary.
If you have more than 10 atypical moles and come from a melanoma-prone family, then you may have Familial Atypical Mole & Melanoma Syndrome (FAMM syndrome).
FAMM syndrome puts you at a much greater risk of developing melanoma and is equivalent to dysplastic nevus syndrome. If you have it, you will need to have very regular skin checks, probably including full body photography.