Increasing incidence of thyroid cancer is due to increased pathologic detection.
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.
Grodski
Simon
S
University of Sydney Endocrine Surgical Unit, Royal North Shore Hospital Sydney, Australia.
Brown
Tani
T
Sidhu
Stan
S
Gill
Anthony
A
Robinson
Bruce
B
Learoyd
Diana
D
Sywak
Mark
M
Reeve
Tom
T
Delbridge
Leigh
L
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