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The Prevalence and Significance of Incidental Thyroid Nodules Identified on Computed Tomography

Yoon, Dae Young MD*; Chang, Suk Ki MD*; Choi, Chul Soon MD*; Yun, Eun Joo MD*; Seo, Young Lan MD*; Nam, Eun Suk MD; Cho, Sung Jin MD; Rho, Young-Soo MD; Ahn, Hwoe Young MD

Journal of Computer Assisted Tomography: September-October 2008 - Volume 32 - Issue 5 - p 810-815
doi: 10.1097/RCT.0b013e318157fd38
Neuroradiology/Head and Neck Imaging: Original Article

Purpose: The purpose of this study was to assess the prevalence of incidental thyroid nodules (ITN) found on computed tomography (CT) of the neck and to determine whether CT characteristics could distinguish malignant from benign thyroid lesions.

Materials and Methods: We retrospectively reviewed CT scans in 734 patients without known thyroid disease (384 men and 350 women; mean age, 49.8 ± 13.7 years). The CT findings of ITN such as size, shape (anteroposterior-transverse diameter ratio [AP/T ratio]), margin, peripheral enhancing rim, intralesional calcification, and attenuation characteristics were analyzed and correlated with ultrasonographic (US) findings.

Results: One hundred sixty ITNs were noted in 123 (16.8%) patients. Of 120 ITNs whose histological diagnoses were available, 15 (12.5%) were malignant. Malignant nodules more frequently showed nodular or rim calcifications (46.7% vs 13.3%; P < 0.0005), AP/T ratio of greater than 1.0 (33.3% vs 9.5%; P < 0.05), and mean attenuation value on contrast-enhanced scan of greater than 130 Hounsfield units (86.7% vs 49.5%; P < 0.05) than benign nodules.

Conclusions: We found at least a 9.4% (15/160) prevalence of malignancy among ITN detected on CT. The further evaluation with US or biopsy should be performed, if an ITN shows CT features suggesting malignancy (calcification; AP/T ratio, >1.0; or mean attenuation value, >130 HU).

From the Departments of *Radiology, †Pathology, and ‡Otorhinolaryngology, Kangdong Seong-Sim Hospital, Hallym University College of Medicine, Seoul, Republic of Korea.

Received for publication June 27, 2007; accepted August 8, 2007.

Reprints: Dae Young Yoon, MD, Department of Radiology, Kangdong Seong-Sim Hospital, Hallym University College of Medicine, 445 Gil-dong Kangdong-Gu, Seoul 134-701, Korea (e-mail:

© 2008 Lippincott Williams & Wilkins, Inc.