Dysplastic nevus

A dysplastic nevus, (or naevus; pl. nevi or naevi) is an atypical melanocytic nevus;^[1] a mole whose appearance is different from that of common moles. Dysplastic nevi are generally larger than ordinary moles and have irregular and indistinct borders. Their color frequently is not uniform and ranges from pink to dark brown; they usually are flat, but parts may be raised above the skin surface. Dysplastic nevi can be found anywhere, but are most common on the trunk in men, and on the calves in women. In 1992, the NIH recommended that the term "dysplastic nevus" be avoided in favor of more descriptive language.^[2]

Cancer

According to the National Cancer Institute, doctors believe that dysplastic nevi are more likely than ordinary moles to develop into a type of skin cancer called melanoma. However, currently, most dermatologists do not believe that dysplastic nevi develop into melanomas.^{[citation needed]} But individuals with multiple dysplastic nevi are at much higher risk for developing melanomas. Because of this, moles should be checked regularly by a doctor or nurse specialist, especially if they look unusual; grow larger; or change in color, or outline; or if any changes occur.

The controversy over the malignant potential of dysplastic nevi is highlighted by the publications and opinions of Dr. Clark and Dr. Ackerman.^[3]. Essentially, Dr. Clark proposed that the melanocytic nevus evolve into a melanoma in stages - benign to dysplastic, then dysplastic to melanoma. Dr. Ackerman refuted this theory, by proposing that you either have a benign nevus, or a melanoma. There is no transition stage; and the melanoma is a melanoma on day one of its development. Today, most dermatologists believe that an individual with multiple dysplastic nevi do not need to have them all removed. The patient and doctor simply need to be exceedingly careful in identifying a melanoma growing among the dysplastic but benign lesions.

Precaution for individuals with dysplastic nevi

A dermatoscope.

A modern polarized dermatoscope.

Self skin exam monthly is very important. Some dermatologist recommend that an individual with either histologic diagnosis of dysplastic nevus, or clinically apparent dysplastic nevi should be examined by an experienced dermatologist with dermatoscopy once a year (or more frequently).

A melanoma showing irregular borders and colour, diameter over 10 mm and asymmetry (ie A, B, C and D.)

To detect melanomas (and increase survival rates), it is recommended to learn what they look like (see "ABCDE" mnemonic below), to be aware of moles and check for changes (shape, size, color, itching or bleeding) and to show any suspicious moles to a doctor with an interest and skills in skin malignancy.^[4]

A popular method for remembering the signs and symptoms of melanoma is the mnemonic "ABCDE":

• Asymmetrical skin lesion.
• Border of the lesion is irregular.
• Color: melanomas usually have multiple colors.
• Diameter: moles greater than 6 mm are more likely to be melanomas than smaller moles.
• Evolution: The evolution (ie change) of a mole or lesion may be a hint that the lesion is becoming malignant.

The E is sometimes omitted, as in the ABCD guideline. A weakness in this system is the D. Many melanomas present themselves as lesions smaller than 6 mm in diameter; and likely all melanomas were melanomas on day 1 of growth, which is merely a dot a millimeter in size. An astute physician will examine all abnormal moles, including ones less than 6 mm in diameter. Unfortunately for the average person, many seborrheic keratosis, some lentigo senilis, and even warts breaks most if not all of the ABCD rules, and can not be distinguished from a melanoma without a trained eye or dermatoscopy.

A recent and novel method of melanoma detection is the "Ugly Duckling Sign" ^[5][6] It is simple, easy to teach, and highly effective in detecting melanoma. Simply, correlation of common characteristics of a person's skin lesion is made. Lesions which greatly deviate from the common characteristics are labeled as an "Ugly Duckling", and further professional exam is required. The "Little Red Riding Hood" sign, ^[7] suggests that individual with fair skin and light colored hair might have difficult to diagnose melanomas. Extra care and caution should be rendered when examining such individuals as they might have multiple melanomas and severely dysplastic nevi. A dermatoscope must be used to detect "ugly ducklings", as many melanomas in these individuals resemble non-melanomas or are considered to be "wolves in sheep clothing"^[8]. These fair skinned individuals often have lightly pigmented or amelanotic melanomas which will not present with easy to observe color changes and variation in colors. The borders of these amelanotic melanomas are often indistinct, making visual identification without a dermatoscope (dermatoscopy) very difficult.

People with a personal or family history of skin cancer or of dysplastic nevus syndrome (multiple atypical moles) should see a dermatologist at least once a year to be sure they are not developing melanoma.

Biopsy

When an atypical mole has been identified, a skin biopsy takes place in order to best diagnose it. Local anesthetic is used to numb the area, then the mole is biopsied. The biopsy material is then sent to a laboratory to be evaluated by a pathologist. A skin biopsy can be a punch, shave, or complete excision. The complete excision is the preferred method, but a punch biopsy can suffice if cosmetic or practical concern (i.e. the patient does not want a scar) prevents it. A scoop or deep shave biopsy is often advocated, but should be avoided due to risk of causing a recurrent nevus, which can complicate future diagnosis of a melanoma.

Some pathologists follow the traditional method of classifying a melanocytic nevus. It is either benign nevus or a dysplastic nevus (Clark's nevus) or a melanoma. Some pathologist follow Dr. Ackerman's philosophy - a nevus is either a benign nevus, or a melanoma.

Most dermatologists and dermatopathologists use a classification scheme devised by the NIH. In this classification, a nevus can be defined as benign, having atypia, or being a melanoma. A benign nevus is read as (or understood as) having no cytologic or architectural atypia. A dysplastic nevus is read as either having or not having architectural atypica, and having (mild, moderate, or severe) cytologic (melanocytic) atypia^[9]. Usually, cytologic atypia is of more important clinical concern than architectural atypia. Usually, moderate to severe cytologic atypia will require further excision to make sure that the margin is completely clear.

The most important aspect of the biopsy report is that the pathologist indicates if the margin is clear (negative or free of melanocytic nevus), or if further tissue (a second surgery) is required. If this is not mentioned, usually a dermatologist or clinician will require further surgery if moderate to severe cytologic atypia is present - and if residual nevus is present at the surgical margin.

Dysplastic nevus syndrome

"Dysplastic nevus syndrome" refers to dysplastic nevi with familial malignant melanoma, or risk factors for it.^[10] Dysplastic Nevus Syndrome is an autosomal dominant hereditary condition which causes the person to have a large quantity of nevi (moles), often 100 or more. There is a propensity for these nevi to become dysplastic in these individuals. Dysplastic nevi are a precursor to malignant melanoma, and these patients are therefore at a higher risk of developing this malignant form of skin cancer.^[11] A slight majority of melanomas do not form in an existing mole, but rather create a new growth on the skin. Nevertheless, those with more dysplastic nevi are at a higher risk of this type of melanoma occurrence.^[12][13] Such persons need to be checked regularly for any changes in their moles and to note any new ones. In 40-50% of cases, the disorder has been linked with germline mutations in the CDKN2A gene, which codes for p16 (a regulator of cell division).

References

External links

• National Cancer Institute: What You Need To Know About Moles and Dysplastic Nevi

See also

• Nevus

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