title: [Distributions of primary nasopharyngeal carcinoma tumor and patterns of skull base erosion detected by magnetic resonance imaging].
abstract: OBJECTIVE
  To evaluate the distributions of primary nasopharyngeal carcinoma (NPC) and the patterns of skull base involvement in NPC patients using magnetic resonance imaging (MRI).
  
  
  METHODS
  After the approval of institutional review board and informed consent, 838 consecutive newly-diagnosed and untreated NPC patients were examined by MRI. Their MR images were reviewed by two independent radiologists.
  
  
  RESULTS
  Among all cases, the incidence rates of superior side and post-superior side involvement were 98.57% (826/838) and 98.21% (823/838) respectively. The differences were not significant between these two sides (P > 0.05). Lateral side erosion was demonstrated in 784 (93.56%) cases. Posterior side was involved in 391 (46.66%) cases. The total incidence rate of skull base involvement was 65.51% (549/838). According to the anatomic site, the pathways of skull base involvement were classified into 5 spreading routes: anterior; superior; super-lateral; super-anterior and super-posterior. According to the incidence rates and the results of chi-square test, the anatomic sites around the nasopharynx were classified into three groups of risk grades: high-risk (≥ 35%), medium-risk (≥ 5% - 35%) and low-risk (< 5%).
  
  
  CONCLUSIONS
  Skull base involvement of NPC spreads stepwise from proximal site to more distal sites. The area of skull base involvement in NPC is classified into high-grade, medium-grade and lower-grade groups respectively. The high and medium-grade groups are related with T3 stage while the lower-grade group T4 stage. Thus T3 stage should be subdivided into T3a and T3b. These schemes may be useful in a more accurate NPC staging and a delineation of clinical target volume for radiotherapy in NPC patients.
authors.affiliation: Imaging Diagnosis & Interventional Center, State Key Laboratory of Oncology in Southern China, Cancer Center, Sun Yat-sen University, Guangzhou 510060, China.
authors.forename: Yi-Zhuo
authors.initials: YZ
authors.lastname: Li
authors.forename: Pei-Hong
authors.initials: PH
authors.lastname: Wu
authors.forename: Zi-Lin
authors.initials: ZL
authors.lastname: Huang
authors.forename: Chuan-Miao
authors.initials: CM
authors.lastname: Xie
authors.forename: Guo-Yi
authors.initials: GY
authors.lastname: Zhang
authors.forename: Ci-Yong
authors.initials: CY
authors.lastname: Lu
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Pei-Qiang
authors.initials: PQ
authors.lastname: Cai
authors.forename: Xue-Wen
authors.initials: XW
authors.lastname: Liu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D009367:Neoplasm Staging; D011859:Radiography; D019291:Skull Base / Q000000981:diagnostic imaging / Q000473:pathology*; D055815:Young Adult