Purpose@#This study evaluated
thyroid cancer risk in a
lung cancer screening population according to the presence of an incidental
thyroid nodule (ITN) detected on low-
dose chest computed
tomography (LDCT). @*
Methods @#Of 47,837 subjects
who underwent LDCT, a
lung cancer screening population according to the National
Lung Screening Trial results was retrospectively enrolled. The
prevalence of ITN on LDCT was calculated, and the
ultrasonography (US)/
fine-needle aspiration (FNA)–based
risk of
thyroid cancer according to the presence of ITN on LDCT was compared using the Fisher exact or
Student t-test as appropriate. @*Results@#Of the 2,329 subjects (
female male =442,285; mean age, 60.9±4.9 years), the
prevalence of ITN on LDCT was 4.8% (111/2,329). The
incidence of
thyroid cancer was 0.8% (18/2,329, papillary
thyroid microcarcinomas [PTMCs]) and was higher in the ITN-positive group than in the ITN-negative group (3.6% [4/111] vs. 0.6% [14/2,218], P=0.009). Among the 2,011 subjects
who underwent both LDCT and
thyroid US, all
risks were higher (P<0.001) in the ITNpositive group than in the ITN-negative group presence of
thyroid nodule on US, 94.1% (95/101) vs. 48.6% (928/1,910); recommendation of FNA according to the American
Thyroid Association guideline and Korean
Thyroid Imaging
Reporting and Data System
guideline , 41.2% (42/101) vs. 2.4% (46/1,910) and 39.6% (40/101) vs. 1.9% (37/1,910), respectively. @*Conclusion@#Despite a higher
risk of
thyroid cancer in the LDCT ITN-positive group than in the ITN-negative group in a
lung cancer screening population , all
cancers were PTMCs. A heavy
smoking history may not necessitate thorough
screening US for
thyroid incidentalomas.