title: Nasal polyps with metaplastic ossification: CT and MR imaging findings.
abstract: BACKGROUND
  Metaplastic ossification is a rare event in nasal polyps. The purpose of this study was to review the computed tomography (CT) and magnetic resonance (MR) imaging findings of nasal polyps with metaplastic ossification.
  
  
  METHODS
  CT (n=5) and MR (n=3) images of five patients (four men and one woman; mean age, 59 years) with surgically proven nasal polyp with metaplastic ossification were retrospectively reviewed. The location and morphologic characteristics of metaplastic ossification were documented as well.
  
  
  RESULTS
  All lesions were seen as lobulated (n=3), ovoid (n=1), or dumbbell-shaped (n=1) benign-looking masses with a mean size of 3.7 cm (range, 2.4-6.5 cm), located unilaterally in the posterior nasal cavity and nasopharynx (n=2), posterior nasoethmoidal tract (n=2), and maxillary sinus and nasal cavity (n=1). Compared with the brain stem, the soft tissue components of all lesions demonstrated isoattenuation on precontrast CT scans, slight hypointensity on T1-weighted MR images, and hyperintensity on T2-weighted MR images. On contrast-enhanced MR images, heterogeneous enhancement with marked peripheral enhancement was seen in two and homogeneous moderate enhancement in one. All lesions contained centrally located radiodense materials on CT scans, the shape of which was multiple clustered in three, single nodular in one, and single large lobulated in one.
  
  
  CONCLUSIONS
  Although rare, metaplastic ossification can occur within nasal polyps. The possibility of its diagnosis may be raised when one sees a benign-looking sinonasal mass with centrally located radiodense materials on CT scans. MR imaging may be useful when mycetoma or inverted papilloma cannot be ruled out on CT scans.
authors: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Kangnam-Ku, Seoul, 135-710, South Korea.
authors: Yi Kyung
authors: YK
authors: Kim
authors: Hyung-Jin
authors: HJ
authors: Kim
authors: Jinna
authors: J
authors: Kim
authors: Seung-Kyu
authors: SK
authors: Chung
authors: Eunhee
authors: E
authors: Kim
authors: Young-Hyeh
authors: YH
authors: Ko
authors: Sung Tae
authors: ST
authors: Kim
mesh_terms: D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008679:Metaplasia / Q000150:complications / Q000175:diagnosis; D008875:Middle Aged; D009298:Nasal Polyps / Q000150:complications* / Q000175:diagnosis*; D009999:Ossification, Heterotopic / Q000150:complications* / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed / Q000379:methods*