title: Distinctive eosinophilic cytoplasmic inclusion bodies in melanocytic nevi: an immunohistochemical and ultrastructural study.
abstract: BACKGROUND
  We sought to further determine the histochemical, immunohistochemical and ultrastructural properties of eosinophilic cytoplasmic inclusion bodies in melanocytic nevi.
  
  
  METHODS
  Skin specimens from four patients with a known diagnosis of conventional melanocytic nevus (3) or Spitz nevus (1) and containing intracytoplasmic eosinophilic inclusion bodies were selected. In addition, melanomas (25), Spitz nevi (10) and blue nevi (4) were examined to determine the frequency of the inclusions.
  
  
  RESULTS
  Inclusions tended to be located in multinucleated melanocytes with abundant vacuolated cytoplasm. In conventional (hematoxylin and eosin-stained) sections, the degree of density and eosinophilia of intracytoplasmic inclusions varied with size. Periodic acid-Schiff, Fontana and Congo red stains showed no reactivity. All bodies were immunoreactive for ubiquitin but negative for tyrosinase, keratin and vimentin. Ultrastructurally, inclusion bodies were non-membrane bound, ranged from 4 to 7 µm, and were comprised of radiating filamentous structures with or without an electron-dense core. Electron probe x-ray microanalysis revealed no significant peaks. None of additional melanomas, Spitz nevi and blue nevi that were evaluated showed similar inclusions.
  
  
  CONCLUSIONS
  The inclusion bodies described herein bear no resemblance to other cytoplasmic inclusion bodies previously described in melanocytic lesions. There is no discernible relationship to melanosomes by ultrastructural analysis. We postulate a relationship with dysfunction of ubiquitin-mediated protein degradation occurring in melanocytes.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Wonwoo
authors.initials: W
authors.lastname: Shon
authors.forename: David A
authors.initials: DA
authors.lastname: Wada
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Gibson
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Flotte
authors.forename: Bernd W
authors.initials: BW
authors.lastname: Scheithauer
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D004801:Eosine Yellowish-(YS); D015726:Giant Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D002479:Inclusion Bodies / Q000648:ultrastructure*; D008544:Melanocytes / Q000378:metabolism / Q000473:pathology; D020460:Melanosomes / Q000648:ultrastructure; D018329:Nevus, Blue / Q000175:diagnosis* / Q000378:metabolism; D018332:Nevus, Epithelioid and Spindle Cell / Q000175:diagnosis* / Q000378:metabolism; D009508:Nevus, Pigmented / Q000175:diagnosis* / Q000378:metabolism; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D013194:Staining and Labeling; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D025801:Ubiquitin; D004801:Eosine Yellowish-(YS)