Benign and malignant thyroid nodules: US differentiation--multicenter retrospective study

Radiology. 2008 Jun;247(3):762-70. doi: 10.1148/radiol.2473070944. Epub 2008 Apr 10.


Purpose: To retrospectively evaluate the diagnostic accuracy of ultrasonographic (US) criteria for the depiction of benign and malignant thyroid nodules by using tissue diagnosis as the reference standard.

Materials and methods: This study had institutional review board approval, and informed consent was waived. From January 2003 through June 2003, 8024 consecutive patients had undergone thyroid US at nine affiliated hospitals. A total of 831 patients (716 women, 115 men; mean age, 49.5 years +/- 13.8 [standard deviation]) with 849 nodules (360 malignant, 489 benign) that were diagnosed at surgery or biopsy were included in this study. Three radiologists retrospectively evaluated the following characteristics on US images: nodule size, presence of spongiform appearance, shape, margin, echotexture, echogenicity, and presence of microcalcification, macrocalcification, or rim calcification. A chi(2) test and multiple regression analysis were performed. Sensitivity, specificity, and positive and negative predictive values were obtained.

Results: Statistically significant (P < .05) findings of malignancy were a taller-than-wide shape (sensitivity, 40.0%; specificity, 91.4%), a spiculated margin (sensitivity, 48.3%; specificity, 91.8%), marked hypoechogenicity (sensitivity, 41.4%; specificity, 92.2%), microcalcification (sensitivity, 44.2%; specificity, 90.8%), and macrocalcification (sensitivity, 9.7%; specificity, 96.1%). The US findings for benign nodules were isoechogenicity (sensitivity, 56.6%; specificity, 88.1%; P < .001) and a spongiform appearance (sensitivity, 10.4%; specificity, 99.7%; P < .001). The presence of at least one malignant US finding had a sensitivity of 83.3%, a specificity of 74.0%, and a diagnostic accuracy of 78.0%. For thyroid nodules with a diameter of 1 cm or less, the sensitivity of microcalcifications was lower than that in larger nodules (36.6% vs 51.4%, P < .05).

Conclusion: Shape, margin, echogenicity, and presence of calcification are helpful criteria for the discrimination of malignant from benign nodules; the diagnostic accuracy of US criteria is dependent on tumor size.

Publication types

  • Multicenter Study

MeSH terms

  • Chi-Square Distribution
  • Diagnosis, Differential
  • Female
  • Humans
  • Male
  • Middle Aged
  • Predictive Value of Tests
  • Regression Analysis
  • Retrospective Studies
  • Sensitivity and Specificity
  • Thyroid Nodule / diagnostic imaging*
  • Ultrasonography