Low Risk of Transformation to Melanoma for Biopsy-Diagnosed Mildly or Moderately Dysplastic Nevi 

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The risk of transformation to melanoma appears very low for biopsy-diagnosed mildly or moderately dysplastic nevi, and routine surgical excision of nevi with a positive biopsy margin may not be indicated. Patients with biopsy-diagnosed moderately-to-severely and severely atypical nevi, however, have a higher risk of melanoma, and in this group, excision may be beneficial to prevent or detect melanoma. These results from a retrospective review of 580 dysplastic nevi specimens were reported in JAMA Dermatology.

The Boston Medical Center Skin Pathology Laboratory database, which receives specimens from community and academic practices throughout the country, was used to identify pathologic diagnoses of dysplastic nevi. For cases reporting a dysplastic nevus with a positive biopsy margin, records were reviewed to see if excision was performed, and if it was, the presence of residual lesion on pathologic examination and final pathologic diagnosis were recorded, as were concordance of biopsy and excision diagnoses, and clinically significant changes in diagnoses with excision.

Nearly all of the cases reviewed were biopsied by shave biopsy technique. “Standard shave biopsy of atypical nevi includes partial-thickness dermis and a 1- to 2-mm margin of normal skin,” the researchers reported. “Overall, 196 of 580 (34%) reported a positive biopsy margin. A positive biopsy margin was more often reported as the degree of atypia worsened (mild, 11%; mild to moderate, 19%; moderate, 40%; moderate to severe, 62%; and severe, 85%) (P < .001 for test of trend).”

Change in Diagnosis

Of the 196 dysplastic nevi with a positive biopsy margin, 127 (65%) were surgically excised, with the frequency of excision following positive biopsy margin increasing with the grade of atypia; 12% for mild, 53% for mild to moderate, 63% for moderate, 81% for moderate, to severe, and 82% for severe (P < .001 for test of trend). Among dysplastic nevi with a positive biopsy margin that were excised, 42 (33%) showed residual nevus and 2 (1.6%) led to a clinically significant change in diagnosis—from moderately-to-severely dysplastic nevi at biopsy to melanoma in situ upon excision. 

“There were not any cases of biopsy-diagnosed mildly or moderately dysplastic nevi that resulted in a clinically significant change in diagnosis upon excision,” the investigators stated.

“The data suggest that biopsied mildly and moderately dysplastic nevi may not require subsequent surgical excision to confirm the diagnosis and are unlikely to harbor associated melanoma in residual cells after biopsy,” the researchers noted. “In contrast, moderately-to severely dysplastic nevi with a positive biopsy margin displayed a 4% rate of melanoma in situ diagnosis upon surgical excision. Moderately-to-severely and severely dysplastic nevi were also most often associated with melanomas. This suggests that in contrast to patients with mildly and moderately dysplastic nevi, patients with moderately-to-severely and severely dysplastic nevi with positive biopsy margins are more likely to benefit from surgical excision for confirmation of diagnosis, melanoma detection, and melanoma prevention.” ■

Reddy KK, et al: JAMA Dermatol 149:928-934, 2013.




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