Do dysplastic moles develop into melanomas?

Dysplastic moles were long thought to be precursors to melanoma. But in most cases, they are harmless and never cause any health issues.

Atypical or “dysplastic” moles are usually irregular, odd-looking moles that can sometimes appear similar to a melanoma.

For many years, they were considered to be pre-cancerous. In other words, it was thought that if an atypical mole was untreated it would eventually develop into a melanoma – similar to the dysplastic cells sometimes discovered on a Pap smear of the cervix. Many patients of our clinic have had multiple dysplastic moles removed as a “precaution” to prevent melanoma. Other patients with dysplastic moles diagnosed at an initial biopsy have had them re-excised with wider margins “just in case”, leaving a much larger scar with a higher rate of complications.

In fact, the word dysplastic is not really suitable for this type of mole, since it does not seem to have any higher risk of developing into melanoma than a normal-looking mole.

A study published in 2012 examined over 100 patients with dysplastic moles diagnosed between 1980-1989. These moles were removed with very narrow margins (less than 0.2mm). The study found no melanomas occurred at the site of excision of the dysplastic mole, with more than 20 years of follow-up of some patients. The authors concluded that dysplastic moles do not need to be re-excised.¹

Other authors have shown that melanomas are no more likely to arise from a dysplastic mole.²

Our approach:

• If a mole appears to be dysplastic with a low risk of it actually being a melanoma, we prefer to perform repeat dermoscopic photography to look for changes that might suggest that it is in fact an early melanoma. If an apparently dysplastic mole has changed after 3 months, we would consider removing it since there is now more suspicion that it could be a melanoma.
• We might perform a spectroscopic or AI image analysis of the mole to obtain further information and assist in our decision of whether to perform excision of the lesion.
• If we remove a suspicious mole and the pathology confirms that it is a dysplastic mole, we would not normally re-excise the mole.
• Patients with a history of dysplastic moles, especially if there are more than one, should have an annual full body skin check.
• If the person has many dysplastic moles, we might recommend total body photography (mole mapping) to document changes and assist earlier detection of new or changing spots.

References

1. Hocker T, Alikhan A, Comfere N et al,  2013.  Favorable long-term outcomes in patients with histologically dysplastic nevi that approach a specimen border
   Journal of the American Academy of Dermatology volume 68, issue 4, pages 545-551, 1 April 2013 https://doi.org/10.1016/j.jaad.2012.09.031
2. Rosendahl C, Grant-Kels J, Que S,  2015.  Dysplastic nevus: Fact and fiction.  Journal of the American Academy of Dermatology, volume 73 issue 3, pages 507-512, 1 September 2015 https://doi.org/10.1016/j.jaad.2015.04.029