Background. A firm and hard thyroid nodule on palpation is known to be associated with an increased risk of thyroid malignancy. Elastography has been introduced to evaluate the tissue hardness objectively. We investigated the clinical implications of elastography as a prognostic factor in patients with papillary thyroid microcarcinoma. Methods. Elastography images were classified according to Rago scores of 1-5. Malignancies with Rago scores of 4 or 5 were considered as "hard" and remaining malignancies as "soft." Clinicopathologic characteristics were compared between patients with hard or soft malignancies according to the extrathyroidal extension and central and lateral lymph node metastasis by using chi-square tests, Fisher's exact test, and independent t tests. Odds ratios with 95% confidence intervals were calculated for evaluating the factors for predicting extrathyroidal extension and central and lateral lymph node metastasis. Results. A hard malignancy on the Rago score was significantly associated with pathologic extrathyroidal extension compared with a soft malignancy (P = 0.001). The odds ratio of a hard malignancy on the Rago score for predicting extrathyroidal extension was 5.060 (95% confidence interval, 1.565-16.358). A hard malignancy on Rago scores was not associated with central or lateral lymph node metastasis. Conclusions. A hard malignancy on the Rago score of elastography was an independent factor for predicting pathologic extrathyroidal extension on pathology.
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