Atypical Mole.

A Mole sent for pathology usually turns out to be a ‘dyplastic nevus’ rather than a melanoma.

What is an Atypical Mole?

You have a mole removed, and the doctor contacts you with the pathology result to inform you that the mole is harmless but ‘looked funny‘ or ‘could have turned into a melanoma.‘ This simply isn’t true.

An atypical Mole (dysplastic nevus) can be thought of as a mole that looks more concerning to both your skin doctor and the pathologist than a simple mole.

Atypical Mole:

  • Is not a ‘normal looking mole.’
  • Is not a melanoma
  • Causes concern for patients
  • Makes the skin cancer doctor stop in their tracks to carefully evaluate the mole with dermoscopy.

Atypical mole may be larger, darker, or have a greater range of colours than a simple mole. The border may be irregular. In other words, atypical mole may have any of the ABCD features of a melanoma. Atypical mole really can look just like a melanoma.

Regular screenings at a skin cancer clinic are key to checking these moles and discovering melanoma as early as possible. Dermoscopy is very helpful although it may still not be possible for the doctor to call a lesion either a melanoma or atypical mole (dysplastic nevus) without a biopsy.

The term atypical mole is used by doctors during a skin check, whilst the term dysplastic mole is used by pathologists.

It is often difficult for pathologists to distinguish a melanoma from a dysplastic nevus. Indeed, a ‘Severely dysplastic nevus’ is usually treated as a melanoma.

The story of a mole that ‘was turning’

Let’s get back to that story where your skin doctor or Dermatologist phones you after a skin biopsy. The pathology reports a dysplastic nevus and you are informed that it ‘might have turned into a melanoma.’

The possibility that a ‘dysplastic nevus’ can turn into a melanoma is very small, and certainly not the reason for having the biopsy. The true interpretation of this story is is that the appearance of the mole at the time of the skin check was concerning to the extent that a biopsy was required to exclude a melanoma.

The World Health Organisation re-classified moles in 2018 to replace the term ‘mildly dysplasic’ with ‘low grade’ and the term ‘severely dysplastic’ to ‘high grade.’ Moderately dysplastic moles would be expected to be low grade most of the time. Australi

What’s the point of grading moles as ‘low grade’ or ‘high grade?’ The appearance of a mole under the microscope is quite subjective. In other words, pathologists often do not agree with each other. A straightforward benign mole or an obvious melanoma area easy, but what about the in-between mole? Pathologists refer to this as a high-grade (or severely dysplastic) mole. There is uncertainty, and the mole will likely need to be re-excised with wider margins.

There is no evidence that dysplastic naevi are, in fact, common precursors of melanoma*

Atypical Moles and Melanoma Risk

Atypical moles are a ‘risk factor’ for developing melanoma. A person with more than 5 Atypical moles has around a ten times greater risk of melanoma than the person with fewer than 5 atypical moles.

A person with large numbers of  ‘Normal’ looking moles is at increased risk of melanoma. The risk of melanoma in a person with more than 100 simple moles is around seven times greater than the person with an average number of moles (around 30).

The big worry is that an atypical mole may in fact be a melanoma. These moles are often biopsied for this reason although dermatoscopic monitoring is an alternative to biopsy.

There is an association between the number of atypical moles a person has and the the thickness of melanoma. This was found in a study of 566 people with atypical moles that was published in 2016. The authors state that “Younger patients should be educated on the increased risk of thicker melanomas that is associated with having more atypical nevi (moles).” It also is appropriate to consider a more frequent skin check.

FAMM syndrome

A person with more than 10 atypical moles in a melanoma-prone family may indicate Familial Atypical Mole & Melanoma Syndrome (FAMM syndrome). The person with FAMM syndrome is at much greater risk of developing melanoma. FAMM syndrome is equivalent to dysplastic nevus syndrome. There will need to be very regular skin checks probably full body photography.

*Always take advice from your doctor

What does  an Atypical Mole Look like?

The following features are often used to determine if a mole is atypical:

  • 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.

Of course the key condition to exclude is a melanoma because the features of a melanoma.