Since their original characterization by Clark and colleagues in 1978, dysplastic nevi have posed a management dilemma, given their position in the gray area between benign melanocytic nevi and malignant melanoma. Even their histologic typing is the subject of debate, with some pathologists preferring to avoid the common grading system of mild, moderate, or severe atypia.
Dysplastic nevi are benign melanocytic tumors containing clonal populations of hyperproliferative melanocytes. Strictly speaking, dysplastic nevus is a histologic diagnosis, characterized by architectural disorder and cytologic atypia. "Atypical nevus" is the clinical correlate, typified by the classic ABCD criteria of asymmetry, border irregularity, color variegation, and size > 6 mm.
Dysplastic nevi are common in people of Northern European descent, with prevalence estimates ranging from 7% to 24%. Although dysplastic nevi may progress to cutaneous melanoma, most lack the genetic mutations characteristic of cutaneous melanoma, such as CDKN2A, TP53, NF1, RAC1, and PTEN.
Malignant transformation of dysplastic nevus to cutaneous melanoma is rare, with one study estimating a dysplastic nevus-to-melanoma transformation rate of 1 in 30,089 nevi in males and 1 in 39,809 nevi in females. Nevertheless, patients with multiple dysplastic nevi and/or a family history of dysplastic nevus syndrome have a greater risk of developing cutaneous melanoma, with relative risk estimates ranging from 1.6 for individuals with one dysplastic nevus to 10.5 for those with five or more.
Given the high prevalence of dysplastic and atypical nevi, most dermatologists opt to monitor patients with multiple atypical nevi, only biopsying those lesions with clinical and dermatoscopic signs of severe atypia. Regardless of the technique (shave, saucerization, punch, excisional), many of dysplastic nevi show positive histologic margins, even in cases with no residual clinical pigmentation. Should all such lesions be re-excised to ensure no chance of recurrence? And what is the risk of opting to follow for any repigmentation instead?
Development of Cutaneous Melanoma From Excised Dysplastic Nevi
To address this practical concern, Kim and colleagues conducted a retrospective multicenter cohort study of 467 moderately dysplastic nevi with positive histologic margins, gathered from 438 patients (193 women and 245 men; mean age, 46.7 years; 96.7% white). Patients were followed for a mean of 6.9 years (range, 3.0-21.3 years) for development of cutaneous melanoma at a biopsy site or elsewhere on the body. This study did not assess severely dysplastic nevi or nevi that were only partially biopsied.
Among the study cohort, 33.2% had a personal history of melanoma, 50.4% had at least one previously biopsied dysplastic nevus, and 23.8% had a family history of melanoma. The primary methods of biopsy were saucerizations or shave excision (46.4%), punch excision (45.3%), or elliptical excision (7.7%). Key study results included:
52.7% of dysplastic nevi were interpreted as mild to moderate, and 47.3% were interpreted as moderate
Histology was positive at the peripheral (89.9%), deep (3.6%), and both (6.5%) margins
After a mean follow-up of 6 years, no melanomas developed at prior biopsy sites
100 patients (22.8%) developed a subsequent primary melanoma at a distant cutaneous site, and three of these patients developed metastatic melanoma
Melanoma risk factors included a history of melanoma (odds ratio [OR], 11.74) and two or more biopsy-confirmed dysplastic nevi (OR, 2.55)
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Cite this: Graeme M. Lipper. Dysplastic Nevi: Monitoring and Management - Medscape - Oct 25, 2018.