Korean J Radiol.  2011 Oct;12(5):559-567. 10.3348/kjr.2011.12.5.559.

Differentiation between Benign and Malignant Solid Thyroid Nodules Using an US Classification System

• Lee YH
• Kim DW
• In HS
• Park JS
• Kim SH
• Eom JW
• Kim B
• Lee EJ
• Rho MH

• KMID: 1116441
• DOI: http://doi.org/10.3348/kjr.2011.12.5.559

Abstract

OBJECTIVE
To evaluate the diagnostic accuracy of a new ultrasound (US) classification system for differentiating between benign and malignant solid thyroid nodules.
MATERIALS AND METHODS
In this study, we enrolled 191 consecutive patients who received real-time US and subsequent US diagnoses for solid thyroid nodules, and underwent US-guided fine-needle aspiration. Each thyroid nodule was prospectively classified into 1 of 5 diagnostic categories by real-time US: "malignant," "suspicious for malignancy," "borderline," "probably benign," and "benign". We evaluated the diagnostic accuracy of thyroid US and the cut-off US criteria by comparing the US diagnoses of thyroid nodules with cytopathologic results.
RESULTS
Of the 191 solid nodules, 103 were subjected to thyroid surgery. US categories for these 191 nodules were malignant (n = 52), suspicious for malignancy (n = 16), borderline (n = 23), probably benign (n = 18), and benign (n = 82). A receiver-operating characteristic curve analysis revealed that the US diagnosis for solid thyroid nodules using the 5-category US classification system was very good. The sensitivity, specificity, positive and negative predictive values, and accuracy of US diagnosis were 86%, 95%, 91%, 92%, and 92%, respectively, when benign, probably benign, and borderline categories were collectively classified as benign (negative).
CONCLUSION
The diagnostic accuracy of thyroid US for solid thyroid nodules is high when the above-mentioned US classification system is applied.

Keyword

Thyroid nodule; Solid, Ultrasound; Fine-needle aspiration; Classification; Malignancy

MeSH Terms

Biopsy, Fine-Needle
Cytodiagnosis
Diagnosis, Differential
Female
Humans
Male
Middle Aged
Predictive Value of Tests
Sensitivity and Specificity
Thyroid Neoplasms/classification/congenital/pathology/*ultrasonography
Thyroid Nodule/classification/pathology/*ultrasonography
Ultrasonography, Interventional

Figure

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  Fig. 1 Five categories for US diagnosis of solid thyroid nodules. A. Malignant. Longitudinal US image of papillary thyroid carcinoma in 42-year-old woman shows marked hypoechogenicity, spiculated margin, microcalcifications, and taller-than-wide shape for nodule. B. Suspicious for malignancy. Longitudinal US image of papillary thyroid carcinoma in 42-year-old woman shows marked hypoechogenicity, smooth margin, and ovoid shape. C. Borderline. Transverse US image of nodular hyperplasia in 60-year-old woman shows macrocalcification in peripheral portion of nodule. Patient underwent right lobectomy of thyroid, despite benign cytology upon US-guided fine-needle aspiration, for pathologic confirmation. D. Probably benign. Longitudinal US image of benign nodule in 57-year-old woman shows isoechogenicity and smooth margin. E. Benign. Longitudinal US image of benign nodule in 46-year-old woman shows ovoid shape, isoechogenicity, and smooth margin.

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  Fig. 2 Metastatic lymphadenopathy of papillary thyroid carcinoma in perithyroidal region. Transverse US image in 27-year-old woman shows associated lymph nodes (arrows) with intranodal cystic components (arrowheads) along both tracheoesophageal grooves in level of upper trachea.

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  Fig. 3 US classification system with 5 categories for diagnosis of solid thyroid nodules.

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  Fig. 4 Receiver-operating characteristic (ROC) analysis. A. Receiver-operating characteristic curves for cut-off US criteria of malignancy. When nodules having 1, 2, or 3 or more malignant US features were considered malignant, Az values were 0.940 (dotted line), 0.950 (dashed line), and 0.931 (dotted and dashed line), respectively. B. Receiver-operating characteristic curve of US classification system when two or more malignant US features were considered as criteria of malignant US diagnosis (Az value: 0.950, confidence interval: 0.914-0.986). Sensitivity, specificity, positive and negative predictive values, and accuracy of US diagnosis were determined to be 86%, 95%, 91%, 92%, and 92%, respectively when malignant and suspicious for malignancy cases were collectively classified as malignant and benign, while probably benign and borderline were collectively classified as benign.

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  Fig. 5 Benign nodule designated as suspicious for malignancy as result of thyroid US in 52-year-old woman (false positive). Longitudinal US image of thyroid nodule in left mid-lobe shows hypoechogenicity, spiculated margin, and round shape (arrow); however, lesion was confirmed as spontaneously collapsed nodule of previous benign cystic thyroid nodule by consecutive US-fine needle aspirations and follow-up US.

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  Fig. 6 Papillary thyroid carcinoma designated as benign from thyroid US in 18-year-old woman (false negative). Longitudinal US image of right thyroid nodule shows ovoid shape, isoechogenicity, smooth margin, and peripheral vascularity (A, B).

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