Certain types of moles increase your risk of developing melanoma.
Lots of Moles
This is defined as having 50 or more small, normal moles, or five or more normal moles of at least 5 millimeters (almost 1/4 inch) in diameter.
- If you have 51-100 moles you are at 3.7 times the risk of developing melanoma than the general population. This is because melanoma often arises in existing moles, so having numerous moles increases the risk.
- If you have more than 100 moles, you are at 7.6 times the risk of developing melanoma than the general population.
Atypical moles (also known as dysplastic nevi) do not look like ordinary moles. They may have some or all of the following characteristics:
- Larger than average (5mm-15mm)
- Irregular or indistinct borders
- Color is variable throughout and may be pink, brown and/or black
- Surface may be bumpy or smooth
- May resemble a fried egg, with a raised center of darker
pigmentation surrounded by a flat, lighter area
- Individuals with dysplastic nevi and no personal and family history of melanoma have a risk 7 to 27 times greater of developing melanoma.
- The risk of melanoma increases significantly if there is a personal or family history of melanoma.
When pathologists or dermatologists see an atypical mole, they will often rate the degree of the atypica as mild, moderate or severe.
- There are no specific guidelines for what should be done to a mole based on the degree of atypica
- Because the vast majority of atypical nevi do not turn into melanoma, it is not standard of care to just remove all of them
- Nearly all dermatologists will remove any severe atypical mole (usual with an extra area of normal skin to make certain it is completely recovered)
- Many dermatologists will re-excise (cut) moderately dysplastic moles, while other dermatologists feel that mildly atypical moles do not need to be cut out and will instead opt to watch them
- Close monitoring is very important, and people diagnosed with atypical nevi should examine their skin for new moles or for changes in existing moles
Dysplastic Nevus Syndrome
Dysplastic nevus syndrome (DNS) also called atypical nevus syndrome (ANS), is when a person develops many more moles than the general population. These syndromes may be acquired or inherited. In the acquired syndrome, there is no family history, in the inherited syndrome, a person comes from a family where others have had this condition.
The condition is defined as:
- Having greater than 50 moles
- At least some of the moles have atypical features, such as irregular borders, colors, etc.
- Having less than 50 moles but at least 5 atypical moles
- People with acquired DNS (who do not have a family history of melanoma) have an increased risk of developing melanoma.
- People with inherited DNS and a family history of melanoma, defined as having more than two first-degree family members (a parent, sibling, or child) have FAMM (Familial Multiple Mole and Melanoma).
- People with FAMM have a very high risk of melanoma, up to 100% by age 80.
Congenital nevi are moles that are present at birth or that appear in early infancy. They are uncommon and only occur in about 1% to 2% of all newborns. (1-3)
|Small||Smaller than 1.5cm diameter|
|Medium||1.5cm to 10cm in diameter|
|Large||Larger than 10cm in diameter|
|Giant||Greater than 20cm in diameter|
The risk of developing a melanoma is directly related to the size of the congenital nevus. Studies that have investigated the risk of a small or medium congenital nevus turning into a melanoma have put the lifetime risk between 0% - 5%.
- The risk for giant nevi (also known as garment nevi) which cover major areas of the head or body is less clear. Historically, some studies reported a very high lifetime risk (up to 50%). Recently, larger studies have placed the lifetime risk at closer to 10% - 12%.
1. Walton RG, Jacobs AH, Cox AJ. Pigmented Lesions in Newborn Infants. Br J Dermatol.1976;95:389-396.
2. Gross BD, Forman D, Ansell PE et al. The Prevalence and Characteristics of Congenital Pigmented Lesions in Newborn Babies in Oxford. Pediatr Perinat Epidemiol. 1990;4:448-457.
3. Rivers JK, Frederiksen PC, Dibdin C. A Prevalence Survey of Dermatoes in the Australian Neonate. J Am Acad Dermatol.1990;23:77-81.
Lots of Moles
If you have lots of moles you are at 3 times greater risk of developing melanoma than the general population.
Having dysplastic nevi alone without a history of melanoma will increase the chances of developing a melanoma.
Individuals with acquired DNS (who do not have a family history of melanoma) have an increased risk of developing melanoma.
Individuals with DNS and a family history of melanoma are at the highest risk of developing melanoma, with a lifetime risk that approaches 100% by age 70.
The risk of developing a melanoma is directly related to the size of the congenital nevus.