title: Primary tumour diameter as a risk factor for advanced disease features of differentiated thyroid carcinoma.
abstract: OBJECTIVE
  To study the relationship between primary tumour size and the risk of advanced disease features (multifocal or locally invasive disease, lymph-node or distant metastases) in differentiated thyroid carcinoma (DTC).
  
  
  METHODS
  A retrospective chart review study.
  
  
  METHODS
  The study sample comprised 935 papillary (PTC) and 291 follicular thyroid carcinoma (FTC) patients treated in our hospital from 1978 to 2007.
  
  
  METHODS
  Kaplan-Meier analyses and log-rank tests were performed to calculate tumour size-adjusted cumulative risk of advanced disease features.
  
  
  RESULTS
  Accounting for primary tumour diameter, there were no significant differences in cumulative risks of multifocal carcinoma (P = 0.12) or distant metastases (P = 0.49) between PTC and FTC. PTC showed higher cumulative risks of local invasion (P < 0.0001) or lymph-node metastases (P < 0.0001). The cumulative risk of tumour multifocality increased 5%/cm of primary tumour diameter. The cumulative risk of local invasion or lymph-node metastases in PTC and of distant metastases in DTC increased exponentially at a threshold tumour diameter of 10 mm. In FTC, lymph-node metastases are associated almost exclusively with primary tumours showing extrathyroidal growth.
  
  
  CONCLUSIONS
  Starting with a 1 cm primary tumour diameter, increasing tumour size is associated with an exponentially increasing risk of local invasion or lymph-node or distant metastases of DTC. The current classification of carcinomas < 2 cm as T1 is therefore questionable.
authors.affiliation: Department of Nuclear Medicine, University Clinic Würzburg, University of Würzburg, Würzburg, Germany. verburg_e@klinik.uni-wuerzburg.de
authors.forename: Frederik A
authors.initials: FA
authors.lastname: Verburg
authors.forename: Uwe
authors.initials: U
authors.lastname: Mäder
authors.forename: Markus
authors.initials: M
authors.lastname: Luster
authors.forename: Christoph
authors.initials: C
authors.lastname: Reiners
mesh_terms: D000328:Adult; D002277:Carcinoma / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009385:Neoplastic Processes; D012189:Retrospective Studies; D012307:Risk Factors; D013964:Thyroid Neoplasms / Q000473:pathology*; D047368:Tumor Burden