title: Langerhans cells and melanocytes share similar morphologic features under in vivo reflectance confocal microscopy: a challenge for melanoma diagnosis.
abstract: BACKGROUND
  Intraepidermal Langerhans cells (ILC) are difficult to differentiate from melanocytes under reflectance confocal microscopy (RCM) and their presence may simulate pagetoid spread of melanocytes on RCM images.
  
  
  OBJECTIVE
  We sought to correlate bright round and dendritic cells in a pagetoid pattern identified on RCM with findings of conventional histopathology and immunohistochemistry for lesions that were falsely diagnosed as melanoma by RCM.
  
  
  METHODS
  This retrospective study included histopathologically proven nevi, imaged by RCM, which displayed bright cells in a pagetoid pattern (BCPP) under RCM, resulting in the incorrect RCM diagnosis of melanoma. Morphological comparisons were made between RCM images of nevi showing BCPP, histopathologically proven melanomas displaying BCPP, and biopsy-proven nevi without BCPP.
  
  
  RESULTS
  We identified 24 nevi that were falsely diagnosed as melanoma by RCM because of the presence of BCPP. These pagetoid cells on RCM corresponded on histopathology to ILC with a high density in 23 of the 24 nevi (95%) and to melanocytes in 7 of the 24 nevi (29%). Among 6 melanomas displaying BCPP on RCM, ILC with high density were observed histopathologically in 5 of the 6 cases (83%) and pagetoid melanocytes were seen in all 6 cases (100%).
  
  
  CONCLUSIONS
  The results cannot be generalized to clinically banal-appearing nevi.
  
  
  CONCLUSIONS
  Although the finding of BCPP is a useful RCM feature for the diagnosis of melanoma, it does not always imply the presence of pagetoid melanocytes but may at times represent ILC.
authors.affiliation: Dermatology Service, Memorial Sloan-Kettering Cancer Center, New York, New York 10022, USA. panteahashemi@gmail.com
authors.forename: Pantea
authors.initials: P
authors.lastname: Hashemi
authors.forename: Melissa P
authors.initials: MP
authors.lastname: Pulitzer
authors.forename: Alon
authors.initials: A
authors.lastname: Scope
authors.forename: Ivanka
authors.initials: I
authors.lastname: Kovalyshyn
authors.forename: Allan C
authors.initials: AC
authors.lastname: Halpern
authors.forename: Ashfaq A
authors.initials: AA
authors.lastname: Marghoob
mesh_terms: D000328:Adult; D001706:Biopsy; D046169:Dermoscopy / Q000379:methods / Q000592:standards; D003937:Diagnosis, Differential; D003951:Diagnostic Errors / Q000517:prevention & control; D005260:Female; D006801:Humans; D007801:Langerhans Cells / Q000166:cytology*; D008297:Male; D008544:Melanocytes / Q000166:cytology*; D008545:Melanoma / Q000473:pathology*; D018613:Microscopy, Confocal / Q000379:methods* / Q000592:standards; D008875:Middle Aged; D009506:Nevus / Q000473:pathology; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000473:pathology*