Size discrepancy between sonographic and pathological evaluation of solitary papillary thyroid carcinoma

Background: Sonographic size of suspicious thyroid lesions is an essential parameter in the evaluation of thyroid nodules, determining the need for needle biopsy and has impact on the extent of surgery. Limited data is available on the correlation between the size of the thyroid nodule on sonography and the actual size measured during histological examination. The aim of the present study was to compare these two modalities and to discuss the potential clinical implications of the findings in the study population. Methods: The database of Rabin Medical Center was reviewed for all patients with histologically proven papillary carcinoma of the thyroid treated by thyroid surgery between 2005 and 2010. Results: 292 patients with papillary thyroid carcinoma were included. The mean sonographic size of the nodule was 2.19 ± 1.15 cm. The mean pathological diameter was 1.69 ± 1.09 cm. Discrepancies between tumor histological diameter and the sonographically measurement were more prominent in tumors larger than 1.5 cm. Nonetheless, 18.8% of thyroid nodules that were measured by US as larger than 1 cm, were found to be smaller than 1 cm on final pathology. Similarly, 7.2% of nodules evaluated by sonography were determined as being larger than 4 cm, while their definitive size was smaller than 4 cm. Conclusions: We noted a significant discrepancy between the preoperative sonographic and the pathologic size measurements for papillary thyroid carcinoma. The sonographic evaluation misclassifies both patients with small and large thyroid tumors, and consequently exposes them to unnecessary workup and more extensive operation. This discrepancy between the ultrasound findings and actual tumor size should be taken into account in clinical practice and help guide the evaluation and treatment of patients with thyroid nodules