Hoang Jenny

MBBS

Duke University Medical Center

Associate Professor of Radiology

NLST (Learn more about this study)

NLST-58

Feb 26, 2014

Incidental Thyroid Nodules and Other Incidental Findings in the NLST

An incidental thyroid nodule (ITN) is defined as a thyroid nodule detected in studies performed for an indication not specific to the thyroid in a patient without known thyroid disease. An ITN is a common finding seen in 1 in 6 patients having CT scans and poses a difficult problem for radiologists and clinicians (1). Despite favorable features of low malignancy rate in ITN of 0.5 to 9% (2-4) and excellent survival for the majority of thyroid cancers, many feel compelled to recommend workup of ITN for fear of missing malignancy. This practice is thought to have contributed to exponential increase in thyroid cancer incidence due to detection of small cancers that would have previously remained asymptomatic and indolent in the patient’s lifetime (5).

There are currently no official guidelines on how to workup ITN seen on CT. This has resulting in variable reporting practices among radiologists (6). Many thyroid nodules may be seen and not reported, but if a thyroid nodule is reported and worked up, this will contribute to additional costs of lung cancer screening. The prevalence of reported and unreported incidental findings has not been estimated. The benefits of detecting incidental but significant findings has not been described.

REFERENCES
1. Nguyen XV, Choudhury KR, Eastwood JD, Lyman GH, Esclamado RM, Werner JD, et al. Incidental Thyroid Nodules on CT: Evaluation of 2 Risk-Categorization Methods for Work-Up of Nodules. AJNR Am J Neuroradiol. 2013 Sep;34(9):1812-7. PubMed PMID: 23557957.
2. Tan GH, Gharib H. Thyroid incidentalomas: management approaches to nonpalpable nodules discovered incidentally on thyroid imaging. Ann Intern Med. 1997 Feb 1;126(3):226-31. PubMed PMID: 9027275. Epub 1997/02/01. eng.
3. Yoon DY, Chang SK, Choi CS, Yun EJ, Seo YL, Nam ES, et al. The prevalence and significance of incidental thyroid nodules identified on computed tomography. J Comput Assist Tomogr. 2008 Sep-Oct;32(5):810-5. PubMed PMID: 18830117. Epub 2008/10/03. eng.
4. Smith-Bindman R, Lebda P, Feldstein VA, Sellami D, Goldstein RB, Brasic N, et al. Risk of Thyroid Cancer Based on Thyroid Ultrasound Imaging Characteristics: Results of a Population-Based Study. JAMA Intern Med. 2013 Aug 26. PubMed PMID: 23978950. Epub 2013/08/28. Eng.
5. Hoang JK, Roy Choudhury K, Eastwood JD, Esclamado RM, Lyman GH, Shattuck TM, et al. An Exponential Growth in Incidence of Thyroid Cancer: Trends and Impact of CT Imaging. AJNR Am J Neuroradiol. 2013 Oct 10. PubMed PMID: 24113469.
6. Hoang JK, Riofrio A, Bashir MR, Kranz PG, Eastwood JD. High Variability in Radiologists' Reporting Practices for Incidental Thyroid Nodules Detected on CT and MRI. AJNR Am J Neuroradiol. 2014 Jan 9. PubMed PMID: 24407274. Epub 2014/01/11. Eng.

1. To determine the rate of significant thyroid abnormalities reported in the CT screening arm of the NLST.

2. To estimate the rate of ITN on CT screening.

3. To describe other significant incidental abnormalities detected in the chest and abdomen in the CT screening arm of the NLST.