title: Diagnostic changes as a reason for the increase in papillary thyroid cancer incidence in Geneva, Switzerland.
abstract: OBJECTIVE
  Several studies have reported upward incidence trends of papillary thyroid cancer. It is unclear whether these trends reflect a real risk increase, by some attributed to iodine supplementation, or an artificial one, due to increased diagnostic activity or changed histological criteria. This study examines if these artificial factors explain the increased papillary thyroid cancer incidence in the Swiss canton of Geneva.
  
  
  METHODS
  All thyroid carcinomas (n = 436) recorded between 1970 and 1998 at the Geneva Cancer Registry were considered. European age-adjusted incidence trends were estimated using linear regression analysis. For papillary cancers we evaluated diagnostic modalities and way of presentation (in particular microcarcinoma < 1 cm or silent carcinoma). In addition, we reviewed the histological slides of follicular carcinomas.
  
  
  RESULTS
  Papillary thyroid cancer incidence increased significantly from 0.7 to 1.8/100,000 for men and from 3.1 to 4.3/100,000 for women between 1970-74 and 1995-98. The proportion of microcarcinomas and silent carcinomas increased from 17% to 24% between 1970-79 and 1990-98. At histological review, follicular cancers were more often reclassified as papillary cancer for cases diagnosed between 1970 and 1979 than for cases diagnosed between 1990 and 1998 (45% vs 25%, p = n.s.).
  
  
  CONCLUSIONS
  The increasing papillary thyroid cancer incidence seems mainly due to changes in histological diagnostic criteria and, to a lesser extent, to increased diagnostic activity. If confirmed, the results of this study indicate that fears of increasing incidence rates of papillary thyroid cancer should not prevent implementation of adequate programs of iodine supplementation in the many areas where iodine deficiency still prevails.
authors.affiliation: Geneva Cancer Registry. Institute for Social and Preventive Medicine, University of Geneva, Switzerland.
authors.forename: Helena M
authors.initials: HM
authors.lastname: Verkooijen
authors.forename: Gerald
authors.initials: G
authors.lastname: Fioretta
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Pache
authors.forename: Silvia
authors.initials: S
authors.lastname: Franceschi
authors.forename: Luc
authors.initials: L
authors.lastname: Raymond
authors.forename: Hyma
authors.initials: H
authors.lastname: Schubert
authors.forename: Christine
authors.initials: C
authors.lastname: Bouchardy
mesh_terms: D000231:Adenocarcinoma, Papillary / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D012042:Registries; D013557:Switzerland / Q000453:epidemiology; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000453:epidemiology*