In a study published in 1997 [Tucker MA et al.
JAMA, 1997; 277:1439-1444] it was found that about half of 716 patients
with newly diagnosed melanoma had numerous dysplastic nevi on the skin.
This large study confirmed observations made since 1978 that there
appeared to be an association between the presence of numerous, large
dysplastic nevi and an increased risk for melanoma. The risk is greater
when other members of the patient’s family have had melanoma.
The authors of this 1997 study calculated risk
associated with dysplastic nevi:
1 dysplastic nevus = 2-fold increased risk for
melanoma
10 or more dysplastic nevi = 14-fold increased
risk for melanoma
They also found increased risk when there is a
large number of normal moles (nevi) on a person’s body: 2-fold
increased risk when moles are small, 4-fold increased risk when there is
a mix of large and small moles.
On the basis of this and other studies, it seems
clear that risk for melanoma is increased in a person with a large
number of nevi, and is particularly increased in a person with one or
more dysplastic nevi. It is important to note that while melanomas can
arise in both common nevi and dysplastic nevi – it is impractical and
unnecessary to remove the overwhelming majority of nevi. Only nevi that
have the clinical appearance of melanoma or those that are changing in
color, shape or size require biopsy. It is important that individuals
with large numbers of nevi or dysplastic nevi be monitored for the
development of melanoma.
How can one assess whether dysplastic nevi are
present?
Anyone with large numbers of moles (more than 50)
or individually large moles (>5mm) should consider seeing a
dermatologist for evaluation for possible dysplastic nevi/atypical
moles. The features that distinguish dysplastic nevi from common moles
is their size (>5m), border (indistinct), and color (often containing
multiple shades of tan, brown, and pink). People with dysplastic nevi
are also more likely to have moles in unusual places such as the scalp,
pubic area, and breasts. Individuals with even a single dysplastic nevus
should seek medical evaluation. The diagnosis of a dysplastic nevus can
often be made without biopsy by experienced clinicians.
Management of patients who have one or more
dysplastic nevi.
Individuals with dysplastic nevi should perform
regular skin self examination (LINK) and use sun protection (LINK).
Dermatologic evaluation permits assessment of a patient’s melanoma
risk and the need for biopsy or excision. Patients at significant
melanoma risk related to the number and appearance of their nevi and/or
because of a personal or family history of melanoma may benefit from
ongoing dermatologic follow up.
