Objective: The Society of Radiologists in Ultrasound (SRU) recommendations on thyroid nodules are intended to "diagnose thyroid cancers that have reached clinical significance, while avoiding unnecessary tests and surgery in patients with benign nodules." The aim of our study was to determine the proportion of thyroid nodules undergoing ultrasound-guided fine-needle aspiration (FNA) that do not meet SRU recommendations.
Materials and methods: This study is a retrospective study of 400 consecutive ultrasound-guided thyroid FNA encounters from July 2010 through June 2011. An encounter was defined as presentation to the department of radiology on a given date for FNA of one or more thyroid nodules. The criteria for performing biopsy of a nodule were determined by the referring clinicians. Nodules were categorized on the basis of sonographic findings as meeting SRU recommendations for biopsy, which we refer to as "SRU-positive," or not, which we refer to as "SRU-negative." Patients without a definitive pathology diagnosis of Bethesda class benign or malignant nodules were excluded. The characteristics of malignancies were compared for SRU-positive and SRU-negative encounters.
Results: The final study group consisted of 360 biopsy encounters for 350 patients and 29 malignancies (8%). Of the 360 biopsy encounters, 86 (24%) were SRU-negative encounters. Malignancy rates in SRU-positive and SRU-negative encounters were 9% (24/274) and 6% (5/86), respectively, and were not significantly different (p=0.5). Eighteen malignancies (75%) in the SRU-positive group were localized, whereas the others had nodal metastases (4/24) or distant metastases (2/24). SRU-positive encounters included medullary carcinoma, anaplastic carcinoma, and melanoma metastasis in addition to papillary carcinoma. All SRU-negative malignancies were localized papillary carcinomas.
Conclusion: One in four thyroid biopsy encounters at our institution did not meet SRU recommendations for biopsy. The application of SRU recommendations reduces the number of benign nodules that undergo workup. Potentially missed malignancies in SRU-negative nodules are less aggressive by histologic type and stage compared with SRU-positive malignancies.