title: Differentiated squamous intraepithelial lesion (dSIL)-like changes in the epidermis overlying anogenital melanocytic nevi: A diagnostic pitfall.
abstract: BACKGROUND
  Differentiated squamous intraepithelial lesion (dSIL) is morphologically and immunohistochemically analogous in the whole anogenital region. dSIL is a premalignant lesion frequently misinterpreted histopathologically as a benign dermatosis. The authors describe a peculiar change in the basal cell layer of the epidermis/epithelium overlying anogenital melanocytic nevi that may histopathologically imitate dSIL. The aim of this study is to familiarize the pathologists with this pitfall to avoid its possible overdiagnosis as dysplasia. Further, we tried to explore the biological characteristics of the dSIL-like changes and to focus on the differential diagnostic aspects.
  
  
  METHODS
  Seventy cases of anogenital nevi were retrieved from our registry. All cases were stained with hematoxylin and eosin (H&E) and reviewed. Cases in which the epidermis overlying nevi featured atypical appearing basal keratinocytes in otherwise fully differentiated epithelium, variable degrees of acanthosis and parakeratosis were selected for additional investigation.
  
  
  RESULTS
  Thirty cases meeting the above described criteria were identified. The patients were 8 males and 22 females, with age at the time of diagnosis ranging from 4 to 68years. Follow-up data were available for 28 patients (range 0.5-19years, mean 5.1), and to date, no signs of epithelial malignancy have been recorded. Immunohistochemically (IHC), the epidermis overlying nevi showed insignificant positivity for p53 in all tested cases. Melanocytic markers (S-100 protein, SOX10, Melan A) and cytokeratin AE1/3 labeled melanocytes and keratinocytes, respectively, enabling their distinction, especially in nevi featuring a junctional component.
  
  
  CONCLUSIONS
  Differentiated squamous intraepithelial lesion-like changes seem to occur relatively often in the epidermis overlying anogenital melanocytic nevi. Since morphologically they are virtually identical to the "true" dSIL, their distinction largely depends on p53 expression in basal keratinocytes with normal p53 expression in dSIL-like changes and diffuse nuclear/p53-null immunostaining in the "true" dSIL serving as an essential differential diagnostic tool. dSIL-like alterations seem to have no malignant potential, as to date, none of the patients included in this study have shown any signs of epithelial malignancy.
authors.affiliation: Department of Pathology, Charles University, Medical Faculty and Charles University Hospital Plzen, Czech Republic. Electronic address: peckova.kveta@gmail.com.
authors.forename: Kvetoslava
authors.initials: K
authors.lastname: Michalova
authors.affiliation: Department of Pathology, Charles University, Medical Faculty and Charles University Hospital Plzen, Czech Republic.
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Kazakov
authors.affiliation: Department of Pathology, Charles University, Medical Faculty and Charles University Hospital Plzen, Czech Republic; Biomedical Center, Faculty of Medicine in Plzen and Charles University Hospital Plzen, Czech Republic.
authors.forename: Michael
authors.initials: M
authors.lastname: Michal
authors.affiliation: Department of Pathology, Charles University, 3rd Medical Faculty and Charles University Hospital Royal Vineyards, Prague, Czech Republic.
authors.forename: Ladislav
authors.initials: L
authors.lastname: Hadravsky
authors.affiliation: Department of Pathology, Charles University, Medical Faculty and Charles University Hospital Plzen, Czech Republic.
authors.forename: Denisa
authors.initials: D
authors.lastname: Kacerovska
authors.affiliation: Cytopathos, Bratislava, Slovakia.
authors.forename: Boris
authors.initials: B
authors.lastname: Rychly
authors.affiliation: Department of Pathology, Charles University, Medical Faculty and Charles University Hospital Plzen, Czech Republic.
authors.forename: Marketa
authors.initials: M
authors.lastname: Miesbauerova
authors.affiliation: Department of Pathology, Charles University, Medical Faculty and Charles University Hospital Plzen, Czech Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Michal
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004817:Epidermis / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008544:Melanocytes / Q000473:pathology; D008545:Melanoma / Q000473:pathology; D008875:Middle Aged; D009506:Nevus / Q000473:pathology*; D009508:Nevus, Pigmented / Q000473:pathology*; D012878:Skin Neoplasms / Q000175:diagnosis / Q000473:pathology*; D065310:Squamous Intraepithelial Lesions of the Cervix / Q000175:diagnosis* / Q000473:pathology*; D055815:Young Adult