Conventional Ultrasonography and Real Time UltrasoundElastography in the Differential Diagnosis of DegeneratingCystic Thyroid Nodules Mimicking Malignancy and PapillaryThyroid Carcinomas

Background: To evaluate the diagnostic utility of conventional ultrasonography and real time ultrasoundelastography in differentiating degenerating cystic thyroid nodules mimicking malignancy from papillarythyroid carcinoma.
Methods: We retrospectively analyzed conventional ultrasonographic and elastographiccharacteristics of 19 degenerating cystic thyroid nodules mimicking malignancy in 19 patients, with 30 surgicallyconfirmed PTCs as controls. Based on size, the nodules had been grouped into less than 10mm (group A) andgreater than 10 mm (group B). We evaluated conventional parameters and elasticity pattern. Color-scaledelastograms were graded as to stiffness of nodules using an elasticity pattern from I (soft) to IV (stiff).
Results:Degenerating cystic thyroid nodules were similar to PTCs in conventional ultrasonographic findings, but theformer frequently showed oval to round in shape (group A, 69.2% vs 18.8%, P=0.017; group B, 66.7% vs7.14%, P=0.017) and punctuate hyperechoic foci (group A, 61.5% vs 0, P<0.001; group B, 50% vs 0, P<0.001).On real time ultrasound elastography, 7 of 13 degenerating cystic thyroid nodules in group A were pattern I,5 were pattern II, 1 was pattern III. One degenerating cystic thyroid nodule in group B was pattern II, 5 werepattern III. The area under the curve for elastography was 0.98 in group A (sensitivity 92.3%, specificity 100%,P = 0.002), and 0.88 in group B (sensitivity 16.7%, specificity 100%, P = 0.014).
Conclusions: As a dependableimaging technique, elastography helps increase the performance in differential diagnosis of degenerating cysticthyroid nodule and malignancy.