Diagnosis of thyroid cancer in children: value of gray-scale and power doppler US.

PURPOSE

To prospectively analyze the accuracy of various diagnostic criteria for cancer in solid thyroid nodules in children on the basis of gray-scale and power Doppler ultrasonographic (US) findings.

MATERIALS AND METHODS

The study protocol was approved by the institutional review board, and patient's parents gave full informed consent. One hundred three consecutive pediatric patients with solid thyroid nodules were included in the study. Thirty-five patients had thyroid cancer (mean age, 14.6 years +/- 2.6 [standard deviation]; range, 10-18 years), and 68 patients had benign thyroid nodules (mean age, 14.2 years +/- 2.9; range 9-18 years). Three-dimensional US was used to determine the volume of thyroid gland and thyroid nodules. Results of nodule cytologic and histologic examination and long-term clinical and US follow-up were used as a proof of final diagnosis. The following US characteristics were evaluated: location, echogenicity, echotexture, outline, presence of a halo, microcalcifications, and type of vascularization. Multivariate logistic regression analysis was used to evaluate the accuracy of US criteria for thyroid cancer in lesions with diameter of 15 mm and smaller and lesions with diameter larger than 15 mm. Qualitative variables were compared by using the chi(2) test and quantitative variables were compared by using the Student t test. Significance was defined at P < .05.

RESULTS

In thyroid nodules with diameter of 15 mm and smaller, the most reliable diagnostic criteria for malignancy were an irregular outline (sensitivity, 69.6%; specificity, 86.4%; P < .001), subcapsular location (sensitivity, 65.2%; specificity, 86.4%; P < .001), and increased intranodular vascularization (sensitivity, 69.6%; specificity, 87.9%; P < .01). For thyroid nodules larger than 15 mm in diameter, the accuracy of US diagnosis was much lower than that for smaller nodules. The only reliable criterion for cancer in this group was hypoechogenicity (sensitivity, 60.0%; specificity, 84.0%; P < .01).

CONCLUSION

Study findings indicate that US is most helpful in diagnosis of thyroid malignancy in thyroid nodules with diameter of 15 mm and smaller, with detection of irregular tumor outline, subcapsular location, and increased intranodular vascularization.