title: Increasing incidence of thyroid cancer is due to increased pathologic detection.
abstract: BACKGROUND
  There has been a marked increase in the incidence of thyroid cancer worldwide over recent decades. Patients with retrosternal goiter (RSG) are not picked up generally by common surveillance techniques such as ultrasound. The aim of this project was to study the incidence of thyroid cancer in patients with RSG.
  
  
  METHODS
  This is a retrospective cohort study. Documented were patient demographics as well as the size, type, and numbers of thyroid cancers. The number of routine histologic blocks examined for multinodular goiter in the different time periods was also examined.
  
  
  RESULTS
  Within a cohort of 13,793 thyroidectomies performed over 40 years, there were 2,260 patients (14%) who underwent surgery for RSG. The percentage of patients with RSG containing thyroid cancer increased from 3.6 to 7.5% (P < .05); however, once papillary microcarcinomas (PMC) (</=10 mm) were excluded there was no increase in cancer incidence (3.4-3.5%, P = .9). The increase in the number of PMC's diagnosed is associated with the increase in the routine number of blocks sampled over the 40-year time period (P < .01).
  
  
  CONCLUSIONS
  This study has confirmed an increase in the incidence of thyroid cancer over 4 decades. However, that increase appears to be due to an increase in the diagnosis of PMC associated with increased sampling of resected specimens by pathologists, raising the possibility that the current epidemic of thyroid cancer may be largely manmade.
authors.affiliation: University of Sydney Endocrine Surgical Unit, Royal North Shore Hospital Sydney, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: Grodski
authors.forename: Tani
authors.initials: T
authors.lastname: Brown
authors.forename: Stan
authors.initials: S
authors.lastname: Sidhu
authors.forename: Anthony
authors.initials: A
authors.lastname: Gill
authors.forename: Bruce
authors.initials: B
authors.lastname: Robinson
authors.forename: Diana
authors.initials: D
authors.lastname: Learoyd
authors.forename: Mark
authors.initials: M
authors.lastname: Sywak
authors.forename: Tom
authors.initials: T
authors.lastname: Reeve
authors.forename: Leigh
authors.initials: L
authors.lastname: Delbridge
mesh_terms: D000231:Adenocarcinoma, Papillary / Q000453:epidemiology* / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001315:Australia; D002648:Child; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D006045:Goiter, Substernal / Q000453:epidemiology* / Q000601:surgery; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000453:epidemiology* / Q000473:pathology*; D055815:Young Adult