title: Inverted papilloma with new bone formation: report of three cases.
abstract: BACKGROUND
  An inverted papilloma (IP) is a benign sinonasal tumor of ectodermal origin, which is locally aggressive and destructive, tends to recur if incompletely removed, and has significant malignant potential. On CT scan, the appearance of an IP is variable and nonspecific but most commonly it appears to have soft tissue density. The association of IPs and new bone formation is extremely rare; to the best of our knowledge, only one case has been reported in the literature to date.
  
  
  METHODS
  We report three cases with existence of bony mass surrounded by polypoid soft tissue diagnosed as IP histopathologically.
  
  
  RESULTS
  The nature, shape, and location of the bony mass were not in concordance with trapped bone, with tumoral calcifications, or with osteoma.
  
  
  CONCLUSIONS
  We propose that with regard to the three cases presented here, new bone formation may be associated with IP pathologically. We also believe that additional investigations are required to characterize the pathophysiological mechanisms involved in neoplasm-induced osteogenesis.
authors.affiliation: Department of Otorhinolaryngology/Head and Neck Surgery, Celal Bayar University Hospital, Turkey. halisunlu@yahoo.com
authors.forename: H Halis
authors.initials: HH
authors.lastname: Unlu
authors.forename: Murat
authors.initials: M
authors.lastname: Songu
authors.forename: Gulgun Yilmaz
authors.initials: GY
authors.lastname: Ovali
authors.forename: Nalan
authors.initials: N
authors.lastname: Nese
mesh_terms: D001842:Bone and Bones / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010012:Osteogenesis; D010016:Osteoma / Q000473:pathology; D013517:Otorhinolaryngologic Surgical Procedures / Q000379:methods; D018308:Papilloma, Inverted / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D010255:Paranasal Sinus Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods