title: Crescent versus rectangle: is it a true negative margin in second and subsequent stages of Mohs surgery?
abstract: BACKGROUND
  The hallmark of Mohs micrographic surgery is using tangential tissue sections that theoretically allow 100% of the tissue margin to be examined, but when taking additional layers for second and subsequent Mohs stages, no detailed methods have been described to ensure that 100% of the tissue margins are analyzed.
  
  
  METHODS
  A rectangular or a crescent-shaped layer is often used to take second and subsequent stages. Here we compare the two techniques for their theoretic advantages and disadvantages.
  
  
  CONCLUSIONS
  The advantage of the rectangular shape has been ease of processing, as well as built in vertical "nicks" that automatically mark the border of the tissue removed, but the rectangular layer may not provide 100% evaluation of the tumor margin because the vertical edges of the rectangular layer are not always completely analyzed, and thus tumor cells cannot be visualized in the vertical margins of these layers. This might result in a false-negative margin reading, which can be avoided by using the crescent layer.
  
  
  CONCLUSIONS
  We propose taking second and subsequent Mohs layers with only a crescent shape, which allows true 100% tissue margin assessment.
authors.affiliation: Department of Dermatology, Boston University School of Medicine, Boston, Massachusetts 02118, USA. emily.yu.2006@gmail.com
authors.forename: Yue
authors.initials: Y
authors.lastname: Yu
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Finn
mesh_terms: D013502:General Surgery / Q000706:statistics & numerical data; D006801:Humans; D015580:Mohs Surgery / Q000379:methods*; D011159:Population Surveillance; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data