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Observation Should be the New Standard for Moderately Dysplastic Nevi

by Todd V. Cartee, MD, FACMS

The management of moderately dysplastic nevi (DN) remains a vexing quandary in clinical practice. Little consensus exists even among experts resulting in a large number of excisions that are potentially unnecessary. Recent surveys demonstrate that a majority of dermatologists choose to re-excise moderately DN with a positive margin on the biopsy.  This occurs because there has essentially been no substantial longitudinal data to guide management decisions.

To address this knowledge gap, 9 institutions participating in the Melanoma Prevention Working Group conducted a retrospective cohort study of cases of moderately DN with positive histologic margins, who were managed with observation and had at least 3 years of follow-up. For eligible cases, the intent of the biopsy had to be complete sampling of the nevus so cases of incisional or partial biopsies were excluded. 467 nevi in 438 patients met inclusion criteria. Remarkably, no cases of melanoma occurred at the site of biopsy. The cohort however was at markedly increased risk of developing a new melanoma at a separate site (22.8%!). Given that the lifetime risk of melanoma in white Americans is 2.6%, this almost 9 fold higher incidence over an average follow-up of only 6.9 years represents an astoundingly increased melanoma risk.  Furthermore, the researchers found that subjects who had a prior melanoma (OR, 11.74; P < .001) or a prior DN (OR, 2.55; P = .01) were at an even higher risk for subsequent melanoma than the overall cohort despite controlling for age, sex, and family history in a multivariate model.

One potential criticism of this study is the absence of homogeneity in grading dysplasia among pathologists.  Concordance rates ranging from 16 to 75% have been reported in prior studies as acknowledged by the authors. A central review was conducted by an independent dermatopathologist of a random sampling of the slides, though this amounted to fewer than 9% of the included nevi. It would seem that the reviewing pathologist was aware that all cases had already received a diagnosis of moderate dysplasia and was asked to confirm that. She agreed with the diagnosis in 87.5% of cases. However, in one case, she upgraded the diagnosis to melanoma in situ. So there does remain concern that one pathologist’s moderately DN is another pathologist’s melanoma, which emphasizes the importance of partnering with an experienced dermatopathology lab. Ultimately, in the future, genetic testing may prove the only reproducible means of identifying malignant melanoma in these challenging cases.

Kim et al. provide cogent evidence to support observation as management of all moderately DN. This may represent a shift in practice paradigm for many dermatologists but should save health care dollars by eliminating numerous unnecessary procedures. In addition, the evidence in this study suggests that patients with a DN should receive regular lifetime total body skin exams for melanoma surveillance. Indeed, clinical follow-up commensurate with patients with a history of thin melanoma may be indicated.