Concordance between thyroid nodule sizes measured by ultrasound and gross pathology examination: effect on patient management

Ultrasound examination (US) is an essential tool in the evaluation of thyroid nodules. The size determined by US is used to distinguish between clinical vs. nonclinical thyroid nodules i.e. greater than or equal to or less than 1 cm. In this study, we evaluated the concordance between the sizes of thyroid nodules measured by US and by gross examination after thyroidectomy. This study included 664 nodules that underwent fine-needle aspiration (FNA) and subsequent excision in 621 patients; 580 had single and 41 patients had multiple (39 with 2, and 2 with 3 nodules) nodules. Both US and gross pathology measurements were taken in three dimensions. The nodule sizes as measured by US were stratified into five groups: A: <or=1.0 cm, B: 1.1-2.0 cm, C: 2.1-3.0 cm, D: 3.1-5.0 cm, and E: >or=5.1 cm. FNA diagnoses were categorized into: Benign (n = 59), Neoplastic / Indeterminate (n = 342), Suspicious (n = 123), Malignant (n = 106), and nondiagnostic (n = 34). Upon excision 278 (42%) nodules were classified as malignant and 386 (58%) as benign. In group A the concordance between US and excisional size was 78.5%, group B 56%, group C 34.5%, group D 40% and group E 52.5%. Only 14 (14/664 2%) nodules measured <or=1.0 cm by US, however, after thyroidectomy 105 (105/664 15.5%) measured <or=1.0 cm in size. Histological diagnoses of this group were benign 62 (58%), papillary microcarcinoma 39 (37%), medullary microcarcinoma 3 (3%) and follicular/Hurthle cell carcinoma 2 (2%) cases. In this study the concordance in benign or malignant nodules measured by US and surgical pathology examination is <or=50%, except in the <or=1.0 cm size range (78.5%). This may lead to an increase in the number of patients undergoing FNA and subsequent surgical excision.