Ashley Hawk Aiken MD, Presenter: Nothing to Disclose

1) Discuss the incidence, significance and natural history of incidental thyroid nodules and differentiated thyroid cancer respectively. 2) Know the current literature and best practice recommendations for further imaging evaluation (US) and FNA of the incidental thyroid nodule. 3) Recognize the indications for cross-sectional imaging in the pre-operative evaluation of thyroid cancer.

The evaluation of thyroid nodules and masses is a broad, complex and controversial topic. This presentation aims to look at the current evidence for three of the most common clinical scenarios: 1. Incidental thyroid nodule on CT or MRI: When to recommend ultrasound or biopsy? 2. Palpable thyroid mass: What is the best test? 3. Preoperative evaluation of a thyroid mass with cancer diagnosis: What is the best test? Thyroid nodules are extremely common, with approximately 50% at autopsy. Most of these nodules are less than a centimeter. Thyroid cancer is also common, but not nearly as common as thyroid nodules, with approximately 2-5% at autopsy. Thyroid cancer incidence is on the rise without a significant change in mortality rate. There is some evidence that a rising incidence of subcentimeter papillary thyroid cancer results from increased detection on CT. There are no current guidelines for the management of these extremely common incidental thyroid nodules. This presentation will review the current literature and suggest some practical guidelines to help radiologists decide how to report these nodules. The combination of size criteria and clinical risk factors such as age is the best approach to date. The common practice of using a 10 mm size threshold alone to recommend US is arbitrary and results in excessive work-up of these incidental nodules, cost and patient anxiety. Current evidence suggests that a stratification approach, incorporating aggressive imaging findings, age younger than 35-40 years, and a 15-mm cutoff for triaging work-up, may reduce this excess work-up of benign ITNs while capturing the same proportion of thyroid malignancies. Ultrasound is the study of choice for the evaluation of an intrathyroidal mass or nodule. CT has no signs that help to differentiate malignant from benign thyroid nodules and is therefore not the study of choice. The Society of Radiologists in Ultrasound (SRU) has developed ultrasound criteria to determine high- risk nodules and prompt fine needle aspiration (FNA) for diagnosis. The SRU recommends FNA for the following US characteristics: 1. 1 cm & microcalcification 2. > 1.5 cm solid or coarse calcifications 3. > 2 cm mixed solid & cystic components 4. Nodule w/ substantial growth 5. Nodule w/ abnormal cervical lymph nodes The American Thyroid association (ATA) guidelines also currently recommend ultrasound as the preoperative study of choice for evaluation of uncomplicated thyroid cancer. However, cross-sectional imaging should be recommended for cases with: 1. Aggressive pathology 2. Clinical signs of extra-thyroidal extension: vocal cord palsy, fixed mass, dysphagia, respiratory symptoms, etc. 3. Lateral compartment lymphadenopathy by palpation or ultrasound Many thyroid cancer experts would also consider cross sectional imaging for ultrasound or palpable central compartment lymphadenopathy.

http://media.rsna.org/media/abstract/2014/14000627/RC606B sec.pdf

Aiken, A, Thyroid Imaging.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14000627.html