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Shear Wave Elastography in Thyroid Nodules with Indeterminate Cytology: Results of a Prospective Bicentric Study.

BACKGROUND
The clinical management of thyroid nodules with indeterminate cytology (IC) remains challenging. The role of shear wave elastography (SWE) in this setting is controversial. The aim of the study was to assess the performances of SWE in terms of prediction of malignancy, reproducibility, and combined analysis with ultrasound (US) examination in thyroid nodules with IC.


METHODS
This prospective study was conducted in two referral centers. Eligible patients had a thyroid nodule ≥15 mm with IC (Bethesda class III-V) for which surgery had been recommended. Patients underwent a standardized US evaluation combined with a SWE exam followed by surgery. SWE parameters included mean (meanEI; kPa) and max (maxEI) elasticity values, and ratio (meanEI nodule/parenchyma).


RESULTS
One hundred and thirty-one nodules (median size 30 mm) in 131 patients were studied. IC was class III in 28%, class IV in 64%, and class V in 8% of cases. After surgery, 21 (16%) nodules were malignant, including nine papillary thyroid cancers (PTC), six follicular thyroid cancers, five poorly differentiated carcinomas, and one large B-cell lymphoma. SWE parameters were similar in benign and malignant nodules, including meanEI (20.2 vs. 19.6 kPa), maxEI (34.3 vs. 32.5 kPa), and ratio (1.57 vs. 1.38). In malignant nodules, meanEI, maxEI, and ratio were higher in the classic PTC variants (n = 4) than in the other PTC variants (n = 5; p < 0.02) and in non-PTC tumors (n = 12; p < 0.005). Intra- and inter-observer coefficients of variations for meanEI in nodules were 23% and 26%, respectively. The French Thyroid Imaging Reporting and Data System score, the American Thyroid Association US classification, and the EU-Thyroid Imaging Reporting and Data System were not associated with malignancy.


CONCLUSIONS
Despite high elasticity values in classic PTC variants, conventional SWE indexes failed to discriminate between benign and malignant tumors in thyroid nodules with IC.