title: MR imaging of nonmalignant polyps and masses of the nasopharynx and sphenoid sinus after radiotherapy for nasopharyngeal carcinoma.
abstract: OBJECTIVE
  The development of a new polyp or mass in the radiation field of a previously treated carcinoma is usually an ominous sign of a recurrent cancer, but rarely may it be caused instead by a nonmalignant process. The purpose of this study was to document the MR appearance of unusual nonmalignant polyps or masses (NMPMs) in the nasopharynx and sphenoid sinus arising after radiation treatment of nasopharyngeal carcinoma.
  
  
  METHODS
  The MR imaging reports of patients undergoing imaging after radiation therapy for nasopharyngeal carcinoma were reviewed retrospectively to identify patients with unusual polyps and masses in the nasopharynx. The MR images of those patients with no evidence of malignancy on biopsy or follow-up were reviewed.
  
  
  RESULTS
  The MR imaging reports of 1282 patients were reviewed, and 11 patients (1%) with NMPMs in the nasopharynx or sphenoid sinus were identified. Two patterns were identified: contrast enhancing nasopharyngeal polyps ranging in size from 1 to 5 cm (n = 5) and sphenoid sinus masses consisting of a nonenhancing mass filling a nonexpanded sinus (n = 4) and a heterogeneous enhancing mass expanding the sinus (n = 2). Osteoradionecrosis produced a large defect in the roof of the nasopharynx causing direct communication with the sphenoid sinus (n = 6). Histology revealed granulation tissue in all of the patients with variable amounts of fibrin and inflammatory cells. A direct infective etiology was not proved in any patient.
  
  
  CONCLUSIONS
  NMPMs in the nasopharynx and sphenoid sinus are rare complications after radiation therapy to the skull base, but the radiologist needs to be aware of their appearance so that they can be considered in the differential diagnosis of suspected tumor recurrence.
authors.affiliation: Department of Diagnostic Radiology and Organ Imaging, Faculty of Medicine, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China. king2015@cuhk.edu.hk
authors.forename: A D
authors.initials: AD
authors.lastname: King
authors.forename: A T
authors.initials: AT
authors.lastname: Ahuja
authors.forename: S-F
authors.initials: SF
authors.lastname: Leung
authors.forename: J
authors.initials: J
authors.lastname: Abrigo
authors.forename: J K T
authors.initials: JK
authors.lastname: Wong
authors.forename: W S
authors.initials: WS
authors.lastname: Poon
authors.forename: K S
authors.initials: KS
authors.lastname: Woo
authors.forename: H S
authors.initials: HS
authors.lastname: Chan
authors.forename: G M K
authors.initials: GM
authors.lastname: Tse
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009298:Nasal Polyps / Q000473:pathology*; D009303:Nasopharyngeal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D009305:Nasopharynx / Q000473:pathology*; D013101:Sphenoid Sinus / Q000473:pathology*