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Color Doppler features of solid, round, isoechoic thyroid nodules without malignant sonographic features: a prospective cytopathological study.

BACKGROUND
No study has examined the malignancy rate and the color Doppler pattern of solid, round, isoechoic thyroid nodules (SRINs) without coexistent malignant sonographic features. We aimed to assess the cytopathological results and color Doppler patterns of SRINs through a prospectively designed study.


METHODS
Between January and December 2010, a total of 727 patients underwent consecutive ultrasound (US)-guided fine-needle aspirations (US-FNAs), and 27 patients who had SRINs with the largest diameter ≥5 mm at US were prospectively selected and enrolled in the study. The color Doppler pattern of each nodule was classified into one of four categories: scant, peripheral, central, or mixed type.


RESULTS
Out of 27 SRINs, 14 were histopathologically confirmed, and 13 were nonsurgically diagnosed by 2 consecutive US-FNAs. Among the 14 surgical SRINs, there were 7 papillary thyroid carcinomas, 2 follicular adenomas, and 5 nodular hyperplasias. All 13 nonsurgical SRINs were finally determined to be benign on the basis of results of US-FNAs and/or long-term US follow-up; thus, the malignancy rate of the SRINs was 25.9% (7/27). There was no significant correlation between the color Doppler pattern and the malignancy rate of SRINs.


CONCLUSION
We recommend that US-FNA should be performed for SRIN to rule out malignancy, regardless of its color Doppler pattern.