title: Bilateral papillary thyroid cancer and associated histopathologic findings.
abstract: OBJECTIVE
  To determine the incidence of bilateral papillary thyroid cancer (PTC) at total thyroidectomy (TT) and compare demographic risk factors (gender and age) and histopathologic findings (tumour size, extrathyroidal extension [ETE], T staging, and multifocality) between patients with PTC in both thyroid lobes and those with PTC limited to the ipsilateral lobe and/or isthmus.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  University teaching hospital.
  
  
  METHODS
  The pathology results of 1047 consecutive patients who underwent TT between 2002 and 2008 were reviewed. Statistical significance was obtained using the chi-square test.
  
  
  METHODS
  Incidence of bilateral PTC and its association with demographic risk factors and histopathologic findings.
  
  
  RESULTS
  Among 592 patients with PTC, 13.2% had bilateral PTC and 86.8% had unilateral and/or isthmian PTC. Bilaterality was present in 12.4% of women and 16.7% of men (p = .24) and in 12.9% of patients aged > or = 45 years and 13.5% < 45 years (p = .83). Bilateral PTC was found in 12.6% of patients with a primary tumour < or = 2 cm and 13.5% > 2 cm (p = .75); 23.6% of tumours with ETE demonstrated bilaterality compared to 9.7% without (p < .0001), and 8.7% of pT1 (p = .08), 9.2% of pT2 (p = .02), 23.0% of pT3 (p < .0001), and 12.5% of pT4 (p = .87) tumours were bilateral, respectively. Among bilateral PTC patients, 43.2% had multifoci in at least one lobe compared to 6.4% when nonbilateral (p < .0001).
  
  
  CONCLUSIONS
  After TT, 13.2% of patients had bilateral PTC. No significant correlation was established between bilaterality and gender, age, and tumour size. Bilaterality was more commonly found in patients with ETE, advanced T stage, and at least one multifocal lobe.
authors.affiliation: Faculty of Medicine, McGill University, Montreal, Quebec. euna.hwang@mail.mcgill.ca
authors.forename: Euna
authors.initials: E
authors.lastname: Hwang
authors.forename: Michael N
authors.initials: MN
authors.lastname: Pakdaman
authors.forename: Michael
authors.initials: M
authors.lastname: Tamilia
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hier
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Black
authors.forename: Louise
authors.initials: L
authors.lastname: Rochon
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Payne
mesh_terms: D002291:Carcinoma, Papillary / Q000473:pathology* / Q000601:surgery*; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D018365:Neoplasm, Residual / Q000473:pathology / Q000601:surgery; D016609:Neoplasms, Second Primary / Q000601:surgery; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000601:surgery*; D013965:Thyroidectomy