title: Carcinoma ex pleomorphic adenoma of the parotid gland.
abstract: BACKGROUND
  Carcinoma ex pleomorphic adenoma (CXPA) is a rare aggressive epithelial malignancy arising from a primary or recurrent benign mixed tumor. Only a few case reports describing the radiologic features of CXPA have been published.
  
  
  OBJECTIVE
  To describe and characterize the magnetic resonance (MR) imaging findings of CXPA in the parotid gland and correlate them with pathologic findings.
  
  
  METHODS
  The MR images of surgically proven CXPA in the parotid gland of five men and five women ranging in age from 28 to 75 years (mean 52 years) were retrospectively reviewed. All MR images were evaluated with emphasis on the size, margin characteristics, extraparotid infiltration, the presence of an encapsulated component, and signal intensity on T2-weighted or short-inversion-time inversion recovery (STIR) images.
  
  
  RESULTS
  The average maximal diameter was 4.3 cm. All 10 tumors had ill-defined boundaries, and seven tumors showed extraparotid infiltration, reflecting invasive growth of the malignant component identified on histological examination. Eight tumors had a round encapsulated component and seven of those signal intensities were a mixture of hypo- and hyperintensity on T2-weighted or STIR images. Histological correlation of these components revealed fibrously encapsulated tumors containing hyalinization and myxoid tissue, suggesting degenerated pleomorphic adenoma. Invasive malignant components had non-specific and various signal intensities.
  
  
  CONCLUSIONS
  An invasive parotid mass co-existing with a round encapsulated component is suggestive of carcinoma ex pleomorphic adenoma.
authors.affiliation: Department of Radiology, Kinki University School of Medicine, Osaka, Japan. kashiwaginobuo@yahoo.co.jp
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kashiwagi
authors.forename: Takamichi
authors.initials: T
authors.lastname: Murakami
authors.forename: Takaaki
authors.initials: T
authors.lastname: Chikugo
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Tomita
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kawano
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Nakanishi
authors.forename: Kazunori
authors.initials: K
authors.lastname: Mori
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Tomiyama
mesh_terms: D008949:Adenoma, Pleomorphic / Q000473:pathology*; D000328:Adult; D000368:Aged; D001707:Biopsy, Needle; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010306:Parotid Gland / Q000473:pathology; D010307:Parotid Neoplasms / Q000473:pathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies