Out, out damned brown fuzzy spot

The Case

The mother of a 13-year-old boy arrives in your office with her son for an urgent visit. She was diagnosed with a malignant melanoma last week, and her mother died from disseminated melanoma 2 years ago. She has mapped 61 acquired moles on her son's trunk, face, and extremities, and many are large with fuzzy borders. She requests your immediate recommendations for management.

Diagnosis: Atypical mole syndrome

The back is the most common location for atypical moles. They are also found in sun-protected areas, unlike most common acquired nevi, which usually appear in sun-exposed areas.² Further, atypical moles are often found in unusual locations like the buttocks, breast, scalp, and iris.

Atypical moles usually begin to develop at puberty and evolve dynamically throughout adulthood, with an increasing or decreasing atypical appearance. They may arise from common melanocytic nevi or emerge de novo. Isolated atypical moles are common in the general population, with the incidence ranging from 2% to 8% in whites.²

The number of melanocytic and atypical nevi are independent risk factors for the development of melanoma; specifically, persons with 5 atypical nevi had a risk 6 times higher than those with no atypical nevi.³ Patients with a history of numerous atypical moles and family members with atypical moles and melanoma may have atypical mole syndrome (AMS) and a high lifetime risk of developing melanoma.

The risk of melanoma in AMS is low in patients with sporadic atypical nevi and no family history but increases with hereditary AMS and family or personal history of melanoma.⁴ One study found that only 26% of melanomas are associated with nevi histologically, 43% of which were classified as atypical or dysplastic.⁵

PATHOLOGY

Histopathologic diagnosis of an atypical nevus is based on cytologic and architectural features. Although there is a direct relationship between the number of atypical clinical features and the percentage of moles with dysplasia, not every clinically identified atypical mole exhibits diagnostic histopathologic features.¹

SCREENING AND PREVENTION

During screening, in addition to the clinical features that characterize atypical nevi, the examiner should look for the "ugly ducklings" -nevi with unusual pigmentation and other features that differ from the patient's characteristic or "signature" moles. Although the patient's signature moles may be atypical, those that are clearly different from the signature moles may warrant a biopsy. Unusually rapidly changing moles with atypical features should also be considered for biopsy.

Screening involves periodic dermatologic exams every 3 to 12 months, based on patient risk, beginning at puberty. Patients and parents should also be educated on self-examination.⁶ It is recommended that screening for patients with family history of AMS begin at 10 years and include scalp, oral mucosa, genital area, and nails.⁷

It is likely that patients with AMS have increased susceptibility to ultraviolet radiation compared to persons without AMS.⁶ Patients should be counseled to avoid prolonged sun exposure, even if using sunscreen, and to use physical protection.⁴