title: Reexamining the Threshold for Reexcision of Histologically Transected Dysplastic Nevi.
abstract: Controversy persists regarding the appropriate management of incompletely excised, biopsy-proven, mild and moderate dysplastic nevi (DN).
  
  
  
  To determine long-term risk of associated melanoma in biopsied mild or moderate DN with positive histologic margins that were clinically observed vs reexcised with negative margins.
  
  
  
  Retrospective cohort study of mixed referral and community patients from an academic pigmented lesion clinic and dermatology clinics of the affiliated Veteran Affairs medical center with biopsy-confirmed DN with positive histologic margins diagnosed from May 15, 1991, to July 8, 2015, and followed up through May 30, 2016. A consecutive sample of 1473 histologically confirmed DN was identified using surgical pathology databases at the study sites; 590 cases in 498 patients met eligibility criteria.
  
  
  
  The primary outcome was the proportion of biopsied DN that progressed to histologically confirmed invasive or in situ melanoma. Secondary outcomes included local nevus recurrence and development of primary melanoma at other anatomic sites.
  
  
  
  The 498 patients had a mean (range) age of 57.6 (14-93) years and 90% were male. Among 590 positive-margin DN, 191 were reexcised and 399 clinically observed without further surgery; 170 reexcised and 304 observed DN had available follow-up data, with mean (SD) follow-up of 5.5 (4.6) years. Cases in the observation group were more likely to demonstrate nevus recurrence than those that were reexcised (3.3% vs 0%; P = .02). Six of 304 (2.0%) observed DN subsequently developed melanoma at the same site, compared with 1 of 170 (0.06%) that were reexcised (P = .43). Five of 6 observed patients who developed melanoma initially underwent partial biopsy with grossly positive margins; 1 melanoma in situ evolved from an excisionally biopsied moderately dysplastic nevus 5 years later. Only 1 case of thin invasive melanoma (≤1 mm) was observed, and no deaths from melanoma arising from biopsy-proven DN occurred through the latest dermatology follow-up. New primary melanoma developed at other sites in 9.9% of excised and 9.4% of resected DN.
  
  
  
  In cases of mild and moderate DN with microscopically positive margins and no concerning clinical residual lesion, observation, rather than reexcision, was a reasonable management option. Partial biopsies of pigmented lesions suspicious for melanoma may lead to delayed melanoma diagnosis and should be discouraged.
authors.affiliation: Dermatology Service, Veterans Affairs Palo Alto Health Care System, Palo Alto, California2Pigmented Lesion and Melanoma Program, Department of Dermatology, Stanford University Medical Center and Cancer Institute, Stanford, California.
authors.forename: Nathaniel H
authors.initials: NH
authors.lastname: Fleming
authors.affiliation: Pathology Service, Veterans Affairs Palo Alto Health Care System, Palo Alto, California.
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Egbert
authors.affiliation: Pigmented Lesion and Melanoma Program, Department of Dermatology, Stanford University Medical Center and Cancer Institute, Stanford, California4Dermatopathology Section, Department of Pathology, Stanford University Medical Center, Stanford, California.
authors.forename: Jinah
authors.initials: J
authors.lastname: Kim
authors.affiliation: Dermatology Service, Veterans Affairs Palo Alto Health Care System, Palo Alto, California2Pigmented Lesion and Melanoma Program, Department of Dermatology, Stanford University Medical Center and Cancer Institute, Stanford, California.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Swetter
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D015331:Cohort Studies; D018450:Disease Progression; D004416:Dysplastic Nevus Syndrome / Q000150:complications / Q000473:pathology / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006787:Hospitals, Veterans; D006801:Humans; D008297:Male; D000072662:Margins of Excision; D008545:Melanoma / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology; D008875:Middle Aged; D012086:Reoperation; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology; D055815:Young Adult