title: Parotid malignancies are not homogenous in terms of their presentation on dynamic MRI - a preliminary report.
abstract: CONCLUSIONS
  At least two groups of parotid malignancies exist, including one whose parameters of dynamic MRI closely resemble those of pleomorphic adenomas. Also tumors with long time to peak enhancement after administration of a contrast agent (Tpeak) and low washout rate (WR) should be considered malignant, especially single masses with concomitant lymphadenopathy located within the deep parotid lobe.
  
  
  OBJECTIVE
  To verify if malignant tumors of the parotid are homogeneous in terms of parameters of preoperative dynamic MRI: Tpeakand WR.
  
  
  METHODS
  The retrospective analysis included 221 surgical patients with parotid tumors. Aside from fine needle biopsy, pre-operative examination included dynamic and diffusion-weighted MRI. Final diagnosis was based on histopathological examination of the surgical specimen.
  
  
  RESULTS
  Twenty-four of 221 (10.8%) malignant lesions were identified. Using k-means clustering based on Tpeakand WR values, two distinct clusters of parotid malignancies were identified. The cut-off value for Tpeakoptimally differentiating between the clusters was 140 s; the cut-off value for WR could not be identified. The two clusters did not differ in terms of dynamic and diffusion-weighted MRI parameters, patient age, sex and prevalence of lymphadenopathy. Significant inter-cluster differences were found in the prevalence of deep parotid lobe involvement and presence of a single mass.
authors.affiliation: a Department of Otolaryngology , Medical University of Gdańsk , Poland.
authors.forename: Bogusław
authors.initials: B
authors.lastname: Mikaszewski
authors.affiliation: b 2nd Department of Radiology , Medical University of Gdańsk , Poland.
authors.forename: Karolina
authors.initials: K
authors.lastname: Markiet
authors.affiliation: c Department of Radiology , University Clinical Center , Gdańsk , Poland.
authors.forename: Aneta
authors.initials: A
authors.lastname: Smugała
authors.affiliation: a Department of Otolaryngology , Medical University of Gdańsk , Poland.
authors.forename: Dominik
authors.initials: D
authors.lastname: Stodulski
authors.affiliation: b 2nd Department of Radiology , Medical University of Gdańsk , Poland.
authors.forename: Edyta
authors.initials: E
authors.lastname: Szurowska
authors.affiliation: a Department of Otolaryngology , Medical University of Gdańsk , Poland.
authors.forename: Czesław
authors.initials: C
authors.lastname: Stankiewicz
mesh_terms: D002277:Carcinoma / Q000000981:diagnostic imaging*; D038524:Diffusion Magnetic Resonance Imaging; D006801:Humans; D008223:Lymphoma / Q000000981:diagnostic imaging; D010307:Parotid Neoplasms / Q000000981:diagnostic imaging*; D012189:Retrospective Studies
keywords: Parotid tumors; cluster analysis; differential diagnostics; dynamic MRI; radiology