Discrepancies between the ultrasonographic and gross pathological size of papillary thyroid carcinomas

PURPOSE: The goal of this study was to investigate the level of agreement between tumor sizes measured on ultrasonography (US) and in pathological specimens of papillary thyroid carcinomas (PTCs) and to identify the US characteristics contributing to discrepancies in these measurements. METHODS: We retrospectively reviewed the US findings and pathological reports of 490 tumors in 431 patients who underwent surgery for PTC. Agreement was defined as a difference of <20% between the US and pathological tumor size measurements. Tumors were divided by size into groups of 0.5-1 cm, 1-2 cm, 2-3 cm, and ≥3 cm. We compared tumors in which the US and pathological tumor size measurements agreed and those in which they disagreed with regard to the following parameters: taller-than-wide shape, infiltrative margin, echogenicity, microcalcifications, cystic changes in tumors, and the US diagnosis. RESULTS: The rate of agreement between US and the pathological tumor size measurements was 64.1% (314/490). Statistical analysis indicated that the US and pathological measurements significantly differed in tumors <1.0 cm in size (P=0.033), with US significantly overestimating the tumor size by 0.2 cm in such tumors (P<0.001). Cystic changes were significantly more frequent in the tumors where US and pathological tumor size measurements disagreed (P<0.001). CONCLUSION: Thyroid US may overestimate the size of PTCs, particularly for tumors <1.0 cm in size. This information may be helpful in guiding decision making regarding surgical extent.