Abstract
Importance
Little evidence exists to guide the management of moderately dysplastic nevi excisionally biopsied without residual clinical pigmentation but with positive histologic margins (hereafter referred to as moderately dysplastic nevi with positive histologic margins).
Objective
To determine outcomes and risk for the development of subsequent cutaneous melanoma (CM) from moderately dysplastic nevi with positive histologic margins observed for 3 years or more.
Design, Setting, and Participants
A multicenter (9 US academic dermatology sites) retrospective cohort study was conducted of patients 18 years or older with moderately dysplastic nevi with positive histologic margins and 3 years or more of follow-up data collected consecutively from January 1, 1990, to August 31, 2014. Records were reviewed for patient demographics, biopsy type, pathologic findings, and development of subsequent CM at the biopsy site or elsewhere on the body. The χ2 test, the Fisher exact test, and analysis of variance were used to assess univariate association for risk of subsequent CMs, in addition to multivariable logistic regression models. To confirm histologic grading, each site submitted 5 random representative slide cases for central dermatopathologic review. Statistical analysis was performed from October 1, 2017, to June 22, 2018.
Main Outcomes and Measures
Development of CM at a biopsy site or elsewhere on the body where there were moderately dysplastic nevi with positive histologic margins.
Results
A total of 467 moderately dysplastic nevi with positive histologic margins from 438 patients (193 women and 245 men; mean [SD] age, 46.7 [16.1] years) were evaluated. No cases developed into CM at biopsy sites, with a mean (SD) follow-up time of 6.9 (3.4) years. However, 100 patients (22.8%) developed a CM at a separate site. Results of multivariate analyses revealed that history of CM was significantly associated with the risk of development of subsequent CM at a separate site (odds ratio, 11.74; 95% CI, 5.71-24.15; P < .001), as were prior biopsied dysplastic nevi (odds ratio, 2.55; 95% CI, 1.23-5.28; P = .01). The results of a central dermatopathologic review revealed agreement in 35 of 40 cases (87.5%). Three of 40 cases (7.5%) were upgraded in degree of atypia; of these, 1 was interpreted as melanoma in situ. That patient remains without recurrence or evidence of CM after 5 years of follow-up.
Conclusions and Relevance
This study suggests that close observation with routine skin surveillance is a reasonable management approach for moderately dysplastic nevi with positive histologic margins. However, having 2 or more biopsied dysplastic nevi (with 1 that is a moderately dysplastic nevus) appears to be associated with increased risk for subsequent CM at a separate site.
This multicenter cohort study examines the outcomes and risk for the development of subsequent cutaneous melanoma in moderately dysplastic nevi excisionally biopsied without residual clinical pigmentation but with positive histologic margins, observed for 3 years or more.
Key Points
Question
Can moderately dysplastic nevi that have been excisionally biopsied with no residual clinical pigmentation but with positive histologic margins (hereafter referred to as moderately dysplastic nevi with positive histologic margins) be closely observed instead of reexcised?
Findings
This multicenter cohort study of 467 moderately dysplastic nevi with positive histologic margins found no cases of cutaneous melanoma at the biopsy site after a mean follow-up time of 6.9 years. However, patients with 2 or more biopsied dysplastic nevi had an increased risk of developing a subsequent cutaneous melanoma at a separate site.
Meaning
Observation of moderately dysplastic nevi with positive histologic margins may be reasonable; however, screening for subsequent cutaneous melanoma at separate sites appears to be warranted for individuals with multiple histologic dysplastic nevi.
Introduction
Owing to a lack of guidelines and a paucity of outcomes data, there is significant variability in the management of histologic dysplastic nevi across the United States. One of the most controversial areas remains whether to observe or reexcise moderately dysplastic nevi excisionally biopsied without clinical residual pigment but with positive histologic margins (hereafter referred to as moderately dysplastic nevi with positive histologic margins). Results of surveys of general dermatologists in Chicago, Illinois, conducted in 2009,1 and in New England, conducted in 2014,2 showed that most of these practitioners (81% in Chicago and 61% in New England) prefer to reexcise moderately dysplastic nevi with positive margins. A recent survey of directors of pigmented lesion clinics in the United States revealed disagreement among expert professionals in the management of these lesions; 51.5% (17 of 33) favored observation and 48.5% (16 of 33) recommended reexcision with margins of at least 1 mm.3
In 2015, the Pigmented Lesion Subcommittee published a consensus statement with the following conclusions: (1) mildly and moderately dysplastic nevi with negative margins do not warrant reexcision, (2) mildly dysplastic nevi biopsied without clinical residual pigment but with positive histologic margins may be safely monitored rather than reexcised, and (3) observation may be a reasonable option for the management of moderately dysplastic nevi with positive histologic margins.4 However, the Pigmented Lesion Subcommittee recommended the acquisition of more data to make definitive recommendations for the clinical care of patients with moderately dysplastic nevi with positive histologic margins.
We report the results of a multicenter retrospective study conducted by members of the Pigmented Lesion Subcommittee on outcomes of moderately dysplastic nevi with positive histologic margins observed for at least 3 years, with confirmation of histologic grading of cases sent by each institution by a central dermatopathologist. Our goal was to address the knowledge gap identified in the Pigmented Lesion Subcommittee consensus statement to help guide future management of moderately dysplastic nevi with positive histologic margins. Incisional or partial biopsies revealing moderately dysplastic nevi were not included in our study because data have demonstrated the potential for histologic misdiagnosis owing to sampling error in these cases.5
Methods
Data Collection
Inclusion criteria for the study were patients who had undergone an excisional biopsy without clinical residual pigment of a nevus with resulting pathologic findings showing moderately dysplastic nevi with positive histologic margins (inclusive of mildly to moderately dysplastic nevi) managed by observation (standard visualization and dermoscopic examinations) for 3 years or more. Given that banal recurrent pigmentation generally occurs within 8 months of a biopsy, and CM has been reported to present as repigmentation more than 20 months after biopsy,6 we chose 3 years as our minimal follow-up interval to ensure that we would not miss cases of CM development owing to insufficient follow-up time. Exclusion criteria were fewer than 3 years of follow-up after the biopsy, incisional or partial biopsy, complete reexcision of the biopsy site, and patient younger than 18 years. Each site conducted a retrospective record review of clinical notes and pathology reports of patients who fit the inclusion and exclusion criteria from January 1, 1990, to August 31, 2014. Atlanta Veterans Affairs Medical Center (Georgia), Beth Israel Deaconess Medical Center (Boston, Massachusetts), Emory University (Atlanta, Georgia), Memorial Sloan Kettering Cancer Center (New York, New York), Palo Alto Veterans Affairs Medical Center (California), Stanford University (California), University of Arizona (Tucson), University of Pittsburgh (Pennsylvania), and University of Utah (Salt Lake City) participated in this study after approval from the institutional review board at each institution. Patient consent was waived by each institutional review board, as all data were deidentified.
The clinical data collected included age at initial biopsy, sex, family history of cutaneous melanoma (CM), personal history of CM, prior biopsied dysplastic nevi, date and location of biopsy, biopsy method (saucerization or shave, punch, or elliptical excision), degree of histologic atypia of dysplastic nevi (mild to moderate or moderate), location of positive margin (lateral, deep, or both lateral and deep), reexcision (yes or no), clinical recurrence of pigment, development of CM at biopsy site, Breslow thickness for any CMs prior to biopsy, development of CM at a separate site, death (yes or no), date of death, last clinical follow-up date, and follow-up source (electronic health record, pathology log, or other). Data on patient phenotype, history, and clinical exposures were also collected when available. Once the data were collected, the study teams shared the deidentified data with Emory University in accordance with each institution’s data use agreement, if required.
Central Dermatopathologic Review of Representative Cases
To confirm the histologic grading of moderately dysplastic nevi across all study sites, a central dermatopathologic review was conducted by a dermatopathologist at an independent site (E.Y.C.) who reviewed 5 deidentified slides or high-resolution digitized slide images of moderately dysplastic nevi included in the study from each site. Participating institutions used the same randomization protocol to select 5 cases of mildly to moderately dysplastic nevi or moderately dysplastic nevi for review. All digitized slide images were uploaded to the Digital Slide Archive viewing platform developed by the Gutman Laboratory at Emory University.7 All sites shared deidentified slides or digitized images in accordance with their institution’s data transfer agreement, if applicable. The grading of dysplastic nevi followed a 5-grade system of mild, mild to moderate, moderate, moderate to severe, and severe based on the degree of cytologic atypia and architectural disorder of the lesion based on criteria set forth by Arumi-Uria et al.8 Specifically, features including lateral circumscription, symmetry, rete ridge distortion, junctional extension, and nuclear size were considered in assigning grades. Any case upgraded to CM was also reviewed by additional dermatopathologists at Emory University and University of Pennsylvania.
Statistical Analysis
Statistical analysis was performed from October 1, 2017, to June 22, 2018, using SAS, version 9.4 (SAS Institute Inc), and SAS macros or software developed at Biostatistics and Bioinformatics at the Winship Cancer Institute.9 Descriptive statistics for each variable were reported. The univariate association of each covariate with the presence of subsequent CM at any site was assessed using the χ2 test or the Fisher exact test, where appropriate, for categorical covariates and analysis of variance for numerical covariates at an α = .05. Two multivariable logistic regression models were developed to elucidate factors significantly associated with the development of CM at the same site as the biopsy of moderately dysplastic nevi with positive histologic margins as well as CM at a separate site. Covariates of interest were age, sex, past medical history of CM, history of prior dysplastic nevi, and family history of CM. All P values were from 2-sided tests and results were deemed statistically significant at P < .05.
In our original consensus statement, we had performed a power calculation that determined that if no melanomas evolved during a prolonged period within a sample size of 2995 dysplastic nevi with positive histologic margins, one would have 95% confidence that the transformation rate was less than 1:1000.4 Given that the analysis in this study for CM at a separate site was secondary and exploratory, no power calculations were performed.
Results
Patient Characteristics
Nine study sites identified 438 patients with 467 moderately dysplastic nevi with positive histologic margins that met inclusion criteria (eTable 1 in the Supplement). Each site contributed at least 3 patients with 3 moderately dysplastic nevi with positive histologic margins. The highest enrolling site contributed 98 patients with 106 moderately dysplastic nevi with positive histologic margins. Table 1 summarizes patient demographics, clinical history, and biopsy characteristics. Of the study cohort, 245 patients (55.9%) were men and the cohort had a mean (SD) age of 46.7 (16.1) years (range, 18-85 years). Of patients with documented clinical data, 96.7% (292 of 302) were white, 33.2% (145 of 437) had a personal history of CM, 50.4% (192 of 381) had prior biopsied dysplastic nevi, and 23.8% (83 of 349) had a family history of CM.
Table 1. Demographic Characteristics and Clinical History of Patients and Characteristics of Biopsied Moderately Dysplastic Nevi.
Characteristic | Patients, No./Total No. (%) |
---|---|
Patients (n = 438) | |
Age, y | |
Mean (SD) | 46.7 (16.1) |
Range | 18-85 |
Sex, No. (%) | |
Male | 245 (55.9) |
Female | 193 (44.1) |
Race/ethnicity | |
White | 292/302 (96.7) |
African American | 1/302 (0.3) |
Asian | 2/302 (0.7) |
Hispanic | 4/302 (1.3) |
Refused to answer | 3/302 (1.0) |
History of biopsied dysplastic nevi | |
Yes | 192/381 (50.4) |
No | 189/381 (49.6) |
History of cutaneous melanoma | |
Yes | 145/437 (33.2) |
No | 292/437 (66.8) |
Family history of cutaneous melanoma | |
Yes | 83/349 (23.8) |
No | 266/349 (76.2) |
Development of cutaneous melanoma after biopsy of moderately dysplastic nevi, No. (%) | |
Same site | 0 |
Separate site | 100 (22.8) |
No | 338 (77.2) |
Development of cutaneous metastatic melanoma after biopsy of moderately dysplastic nevi, No. (%) | |
Yes | 3 (0.7) |
No | 435 (99.3) |
Moderately Dysplastic Nevi (n = 467) | Dysplastic Nevi, No./Total No. (%) |
Anatomic site | |
Head | 20/466 (4.3) |
Neck | 2/466 (0.4) |
Upper extremity | 24/466 (5.2) |
Lower extremity | 80/466 (17.2) |
Trunk | 324/466 (69.5) |
Groin or buttocks | 16/466 (3.4) |
Nevus size, mm (n = 79) | |
Mean (SD) | 5.7 (2.5) |
Range | 2-15 |
Biopsy type | |
Shave | 216/466 (46.4) |
Punch | 211/466 (45.3) |
Elliptical excision | 36/466 (7.7) |
Other | 3/466 (0.6) |
Degree of atypia, No. (%) | |
Mild to moderate | 246 (52.7) |
Moderate | 221 (47.3) |
Positive margin location | |
Peripheral | 346/385 (89.9) |
Deep | 14/385 (3.6) |
Peripheral and deep | 25/385 (6.5) |
Follow-up, y | |
Mean (SD) | 6.9 (3.4) |
Range | 3.0-21.3 |
Clinical recurrence of pigmentation | |
Yes | 3/251 (1.2) |
No | 248/251 (98.8) |
Biopsy Characteristics
The mean (SD) follow-up time for the 467 biopsies was 6.9 (3.4) years (range, 3.0-21.3 years) (Table 1). Most (69.5% [324 of 466]) of the biopsies were located on the trunk. The mean (SD) reported nevus size was 5.7 (2.5) mm (range, 2-15 mm). Of the 466 biopsy techniques, 46.4% (216 of 466) were saucerizations or shave excisions, 45.3% (211 of 466) were punch excisions, and 7.7% (36 of 466) elliptical excisions. Pathology reports showed that 52.7% of dysplastic nevi (246 of 467) were interpreted as mild to moderate and 47.3% (221 of 467) were interpreted as moderate. Regarding histologically positive margins, 89.9% (346 of 385) were positive at the peripheral margins, 3.6% (14 of 385) at the deep margins, and 6.5% (25 of 385) at both peripheral and deep margins.
Development of CM at the Biopsy Site
After a mean (SD) follow-up time of 6.9 (3.4) years, no cases of CM occurred at the biopsy site of the 467 moderately dysplastic nevi with positive histologic margins. The rate of clinical recurrent pigmentation at the biopsy site was 1.2% (3 of 251).
Development of CM at a Separate Site
Of the 438 patients in our study with moderately dysplastic nevi with positive histologic margins, 100 (22.8%) developed a subsequent primary CM at a separate site from the original moderately dysplastic nevi with positive histologic margins during the follow-up period. Three of these patients (0.7%) developed metastatic CM, 2 of whom had invasive CM prior to biopsy of their moderately dysplastic nevi and 1 of whom developed invasive CM after the biopsy; however, data on Breslow depth or other features of those CMs were not included in the collected data. Of the 100 patients with a new primary CM, 93 were alive at follow-up, 5 were deceased, and 2 were listed as unknown.
Risk Factors for Subsequent CM at Separate Site
Factors associated with the risk for subsequent CM at a separate site by univariate analyses are summarized in Table 2. Patients who developed a subsequent CM were older than those who did not (mean [SD] age, 49.7 [15.8] years vs 45.9 [16.9] years; P = .04). In addition, patients who developed a subsequent CM were more likely to have a prior CM (71 of 145 [49.0%] vs 29 of 292 [9.9%]; P < .001) and a prior biopsied dysplastic nevus (64 of 191 [33.5%] vs 25 of 190 [13.2%]; P < .001). A patient’s sex and family history of CM were not statistically associated with risk for subsequent CM. Multivariate logistic regression revealed that prior CM (odds ratio, 11.74; 95% CI, 5.71-24.15; P < .001) and biopsy-proven dysplastic nevi prior to the moderately dysplastic nevi with positive histologic margins (OR, 2.55; 95% CI, 1.23-5.28; P = .01) were independently associated with subsequent CM at a separate site, even after adjusting for sex, family history of CM, and age (Table 2).
Table 2. Univariate and Multivariate Logistic Regression Models for Development of CM at Any Future Site Separate From the Biopsy of Moderately Dysplastic Nevi.
Variable | CM at Separate Site | ||||
---|---|---|---|---|---|
Univariate Model (N = 438) | Multivariate Model (N = 317) | ||||
Yes | No | P Value | OR (95% CI) | P Value | |
Sex, No./total No. (%) | |||||
Male | 56/245 (22.9) | 189/245 (77.1) | .99 | 0.92 (0.46-1.83) | .81 |
Female | 44/193 (22.8) | 149/193 (77.2) | 1 [Reference] | ||
History of CM, No./total No. (%) | |||||
Yes | 71/145 (49.0) | 74/145 (51.0) | <.001 | 11.74 (5.71-24.15) | <.001 |
No | 29/292 (9.9) | 263/292 (90.1) | 1 [Reference] | ||
History of dysplastic nevi, No./total No. (%) | |||||
Yes | 64/191 (33.5) | 127/191 (66.5) | <.001 | 2.55 (1.23-5.28) | .01 |
No | 25/190 (13.2) | 165/190 (86.8) | 1 [Reference] | ||
Unknown | 11/57 (19.3) | 46/57 (80.7) | |||
Family history of CM, No./total No. (%) | |||||
Yes | 24/83 (28.9) | 59/83 (71.1) | .12 | 1.63 (0.82-3.22) | .16 |
No | 52/266 (19.5) | 214/266 (80.5) | 1 [Reference] | ||
Unknown | 24/89 (27.0) | 65/89 (73.0) | |||
Age, mean (SD), y | 49.7 (15.8) | 45.9 (16.9) | .04 | 0.99 (0.97-1.01) | .37 |
Abbreviations: CM, cutaneous melanoma; OR, odds ratio.
Central Dermatopathologic Review Across Study Sites
A total of 40 slides were reviewed because the cases from 2 sites were pooled owing to low numbers. The reviewing dermatopathologist agreed that 35 of 40 of the study cases represented lesions within the spectrum of mildly to moderately dysplastic nevi or moderately dysplastic nevi. Thus, we determined that the rate of capture of eligible samples was 87.5%. Of the remaining cases, 5% (2 of 40) were interpreted as mildly dysplastic nevi and 5% (2 of 40) were interpreted as moderately to severely dysplastic nevi. A single case was interpreted as melanoma in situ. Review of this case with the host institution revealed that the patient had not had a clinical recurrence at the biopsy site after 5 years of clinical follow-up.
Discussion
To our knowledge, this multicenter retrospective observational study of 467 moderately dysplastic nevi with positive histologic margins represents the largest of its kind to date. To investigate possible impairment of the study by the smaller number of cases than the proposed sample size, we performed a post hoc power calculation. Based on the 438 patients, the study was powered to produce a 1-sided 95% CI with a distance from the observed sample proportion (0%) to an upper limit of 0.5%. Thus, when we project the study findings to the entire population, we expect the rate of CM at the biopsy site to be less than 5 of 1000, with a 90% chance. Clinically, we feel comfortable to claim that, with an observed incidence rate of less than 0.5% and a mean of 6.9 years of follow-up, it is unlikely for a CM to develop at the site of a moderately dysplastic nevus with positive histologic margins, thus supporting the 2015 Pigmented Lesion Subcommittee consensus recommendation that observation is a reasonable management option for moderately dysplastic nevi with positive histologic margins.4
Several studies have investigated the outcomes of recurrence and biopsy site CMs in observed dysplastic nevi with positive margins.5,10,11,12,13 Only Hocker et al12 and Hiscox et al13 specified cases of moderately dysplastic nevi with positive histologic margins, reporting a total of 82 such cases without any resulting in CM. Adding the 467 cases from our study, no biopsy site CM developed in 549 unique cases of moderately dysplastic nevi with positive histologic margins (Table 3). Fleming et al5 described a single case of an excisionally biopsied mildly dysplastic nevi in which an atypical intraepidermal melanocytic proliferation, favoring melanoma in situ lentigo maligna type, developed 5 years later at the biopsy site. This finding underscores the need for continued monitoring of patients with biopsied dysplastic nevi. However, one should be reassured in this case that melanoma in situ, by definition, confers low risk of death.
Table 3. Summary of Recent Studies Examining Outcomes of Excisionally Biopsied Moderately Dysplastic Nevi With Positive Histologic Margins.
Source | Excisional Biopsy Only | Moderately Dysplastic Nevi With Positive Margins Observed, No. | Dysplastic Nevi Observed With Positive Margins, Total No. | Duration of Follow-up in Study, Mean, y | Clinically Recurrent Moderately Dysplastic Nevi, % | Excisionally Biopsied Moderately Dysplastic Nevi With CM at Same Site, No./Total No.a | Patients With Subsequent CM at Separate Site, % |
---|---|---|---|---|---|---|---|
Hocker et al,12 2013 | Yes | 42 | 115 | 17.4 | NA | 0/42 | NA |
Hiscox et al,13 2017 | No | 147 | 147 | 3.6 | 4 | 0/40 | NA |
Current study | Yes | 467 | 467 | 6.9 | 1.2a | 0/467 | 22.8 |
Abbreviations: CM, cutaneous melanoma; NA, not applicable.
Of 251 moderately dysplastic nevi for which recurrence data are available.
Our recurrence rate for moderately dysplastic nevi with positive histologic margins was 1.2%, lower than Hiscox et al13 (4% of moderately dysplastic nevi), Goodson et al11 (3.6% of mildly to moderately dysplastic nevi), and Fleming et al5 (3.3% of mildly to severely dysplastic nevi). Our study excluded incisional biopsies with residual pigment, while these other studies did not, suggesting that lesions biopsied with a lower burden of residual melanocytic cells are less likely to recur than those with more residual cells, as seen in incisionally biopsied lesions. Biopsy technique may also be related to our lower recurrence rate. Goodson et al11 found that the shave biopsy technique was statistically associated with higher rates of recurrence. Our study had a lower percentage of shave biopsies in our cohort (46.4%) compared with that reported by Hiscox et al13 (100%).
As a secondary exploratory aim, our study also assessed histologic moderately dysplastic nevi as a factor associated with subsequent CM elsewhere on the body. Of our 438 patients, 22.8% developed CM at another location after biopsy of their moderately dysplastic nevi. Although prior CM was the factor most strongly associated with developing a CM at a separate site (odds ratio, 11.74), our findings suggest that the presence of 2 or more biopsied dysplastic nevi (1 of which is moderately dysplastic) conveyed twice the odds of developing a future CM at a separate site. This finding remained significant even after adjusting for history of CM. Prior studies have focused largely on clinically atypical nevi and risk of future melanoma,14 while in contrast, we explored the role of histologically confirmed dysplastic nevi. Our findings reinforce the need for regular skin examinations and patient education for those with a history of CM and/or 2 or more biopsied dysplastic nevi (at least 1 of which is moderately dysplastic).
We conducted a central dermatopathologic review of dysplastic nevi, which ensured high adequacy of capture (87.5%) because of prior evidence demonstrating poor concordance between pathologists grading dysplastic nevi (ranging from 16% to 75% and κ coefficients of 0.055-0.7115,16,17,18). We did not report another κ coefficient because agreement statistics are used when trying to compare raters who have the same range of possible rankings. Ratings by the institution were binary (yes or no eligible), and the possible rankings for the central review were 5 levels of dysplasia.
The decision to manage moderately dysplastic nevi with positive histologic margins with observation may also be affected by several clinical factors. First, the degree of clinical concern for the biopsied lesion (pretest probability) may play a role in management; if a clinician has a strong concern for CM, the clinician may elect to reexcise even moderately dysplastic nevi with positive histologic margins. Second, if the patient is unable to self-monitor or is unlikely to follow up, a clinician may favor reexcision. However, if the clinical concern for CM is low, if patient self-monitoring is possible, and if clinical follow-up is likely, then we recommend that moderately dysplastic nevi with positive histologic margins may be clinically observed. Importantly, as with any other nevus biopsy site, both patient and clinician should continue to observe the area for suspicious regrowth.
Limitations
We had several limitations to our study. Although we aimed to collect 2995 cases with 3 or more years of follow-up according to our 2015 Pigmented Lesion Subcommittee consensus statement,4 we believe that we fell short of this mark for several reasons: (1) the participating institutions had high rates of full-thickness excisional biopsy techniques (punch and elliptical) with negative histologic margins, (2) observation may have been a more recent management approach for dysplastic nevi with positive margins for some institutions, and (3) some institutions were unable to participate because their dermatopathologists do not report grades of atypia for dysplastic nevi. However, our post hoc power analysis demonstrated acceptable confidence (95%) with a reasonable malignant transformation rate (<0.5%). Another limitation of our study is its retrospective nature, which may have introduced latent biases and confounding by indication. The retrospective nature of our multi-institutional study also precluded concordance tests to assess fidelity of observations across study sites. In addition, any patient who may have developed a CM at a biopsy site within 3 years would not be accounted for because medical records were reviewed only if they had at least 3 years of clinical follow-up. Missing data across study sites in regard to phenotype and exposure factors (eg, UV radiation exposure, tanning bed use, immunosuppression, and phototherapy), prevented in-depth analysis of more variables relevant to the risk of CM (eTable 2 in the Supplement). Family history was not strongly correlated with the development of subsequent CM. This finding may be owing to limitations of patient-reported family history, missing data in 89 patients, and data collection that did not specify first-degree relatives only. Despite these limitations, the data from our study are still compelling, given that it is the largest cohort of moderately dysplastic nevi (n = 467) observed to date, with a substantial follow-up time (6.9 years) and a diverse geographic distribution of the 9 participating institutions.
Conclusions
Our data support observation as a reasonable management approach for moderately dysplastic nevi excisionally biopsied but with positive histologic margins. Our data also support a second recommendation, that patients with a history of CM and/or 2 or more biopsied dysplastic nevi (1 of which is moderately dysplastic) be monitored closely with routine self-examinations and clinical skin examinations, given the increased risk of developing a subsequent CM at a separate site compared with those without this history. In contrast to previous studies examining clinically atypical nevi as a potential variable associated with CM, our exploratory analysis of the development of CM at a separate site specifies the risk of CM with histologic dysplastic nevi, with specific level of dysplasia (at least 1 moderate) and number of dysplastic nevi (at least 2). These data underscore the fact that dysplastic nevi are not obligate precursors of CM but, instead, represent a surrogate risk factor for future CM development. Our recommendation for close observation of moderately dysplastic nevi with positive histologic margins may save patients the morbidity of reexcision, while our recommendation for surveillance for patients with 2 or more biopsied dysplastic nevi (of which 1 is moderately dysplastic) may facilitate early detection or prevention of future CM. Both recommendations have the potential to significantly reduce the health care cost and resource burden associated with reexcisions and CM diagnosis.
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