Dysplastic Nevi - "Funny looking Moles"

Many patients present to a plastic surgeon’s office concerned about a “mole”. The most important diagnostic exclusion is that of melanoma. With regard to this, the diagnosis of a “mole” as a dysplastic nevus (pl. nevi) is important.

What is a dysplastic nevus ?

A dysplastic nevus is defined as a pigmented area, (a “mole”) with clinical and histological features of concern and which may be associated with an increased risk of melanoma.

What does it look like ?

Dysplastic nevi are pigmented, ranging from light brown to very dark. They are usually flat around the edges with a raised central area and are described as having a fried-egg appearance. They are usually more than 5mm in greatest diameter and have irregular, fuzzy edges.

  

The photo above is a bopisy proven dysplastic nevus and the picture below shows a fried egg to emphasize the occasional central papule

Where do they occur ?

Dysplastic nevi occur in up to 10% of the population. Patients may be born with them, but they usually increase in number during puberty. New nevi may also occur in adult life. They can occur anywhere on the body (even on the breasts or buttocks which are usually covered with 2 layers of clothing), although they usually occur on the intermittently sun-exposed areas such as the back. They may be “dysplastic” at their first appearance or they may develop more atypical features with time, especially in “moles” with a “junctional component”.

Above is a schematic diagram of normal skin and below shows how the melanocytes are present below and above the dermo-epidermal junction - so called "junctional nevi"

What is the risk attached to a dysplastic nevus ?

Dysplastic nevi are associated with an increased risk of melanoma – 15 times higher than patients without them. If a patient has dysplastic nevi AND has had a melanoma before, the risk of another melanoma is 100 times higher than the normal. If a patient with a dysplastic nevus has had a melanoma before, and has a first degree relative with a melanoma, their risk of another melanoma rises to 1500 times more than the normal.

Melanoma arises within a dysplastic nevus in about 50% of cases (44-80% in different studies). This means that the other 50% of melanomas come from otherwise normal looking skin. Each dysplastic nevus however, has only a 1 in 10 000 case of becoming a melanoma – a very low risk.

What to do about them?

Having dysplastic nevi is a melanoma risk, but each nevus is actually low risk.

This means that simply cutting them out will only reduce the risk for that patient very marginally. Most international guidelines do not support prophylactic excisions.

Self-examination is cheap and non-invasive and is often recommended despite the lack of scientific evidence.

Genetic screening for CDKN2A mutations is a promising avenue to screen at risk patients, but correlation with melanoma risk is not perfect and it is expensive and is thus not recommended except in the context of clinical trials.

Ocular examination (examination of the retina, done by an ophthalmologist) has been associated with an earlier detection of melanoma of the retina and annual screening in at risk patients is recommended.

The most important screening tool is digital epiluminescent microscopy (mole-max or mole mapping) done by a dermatologist. It gives a much clearer view than can be achieved with the naked eye and stores the digital image for future reference. “Moles” that are suspicious are then referred to the plastic surgeon for excision. This method improves the diagnostic yield and limits unnecessary surgery, while providing the optimal risk management for these patients.

 These two photos show the MoleMax machine and a screen shot from the device

Sunscreen use has been associated with lower numbers dysplastic nevi and should form part of the risk management strategy for patients.

My Personal Recommendation :

1. All patients should perform monthly self-examination of their “moles”.

2. All patients should wear sunblock with SPF 30 or greater every day. Additional clothing cover should be used whenever possible.

3. At risk patients should be screened with a mole-max scan annually. Any suspicious moles should then be excised.

4. An ocular examination should be done every 2 years, except in higher risk patients, when it should be done annually.

5. If a particular “mole” bothers the patient, then I remove it.

Best Regards

Marshall