The purpose of this observational chart review study is to evaluate the efficacy and safety of Radiofrequency Ablation (RFA) for treatment of indeterminate thyroid nodules before and after RFA procedure. This is a data collection study in which the investigators ask patients to give access to information generated before and after RFA treatment of their condition. The RFA procedure uses image guidance to place an electrode through the skin into the target area. In RFA, high-frequency electrical currents are passed through an electrode, creating a small region of heat to treat the lesion.

In the United States, there is an estimated 10% lifetime probability for developing a thyroid nodule.

Up to 15% of these nodules will prove to be malignant. The incidence of thyroid cancer is increasing and is the third leading cause of cancer in women; accordingly, identification of a nodule

1 cm or larger in diameter often prompts a sophisticated diagnostic evaluation comprised of sonographic pattern risk assessment combined with fine needle aspiration biopsy (FNAB), which enables the assessment of cellular morphologic features that could not be identified by means of clinical assessment or imaging. Ultrasound-guided FNAB has been shown to accurately classify 62-85% of thyroid nodules as benign, thereby avoiding diagnostic surgery. Yet, 20-30% of aspirations still yield indeterminate cytologic findings: "atypia (or follicular lesion) of undetermined significance," "follicular neoplasm or suspicious for follicular neoplasm," and "suspicious for malignancy with a risk of malignancy ranging from 6-75%." Most patients with cytologically indeterminate nodules are referred for diagnostic thyroid surgery, but the majority prove to have benign disease. For these patients, thyroid surgery is unnecessary, yet it exposes them to 2-10% risk of serious surgical complications, and most would require thyroid hormone replacement therapy for life. Research in recent years has focused on the potential of molecular diagnostic approaches that could capitalize on increasing knowledge of the molecular etiology of thyroid nodules and the transcriptional and mutation landscape of thyroid cancers to augment diagnostic accuracy of FNABs. Most molecular profiling tests demonstrate a high sensitivity and negative predictive value that helps to decrease the number of benign nodules undergoing unnecessary diagnostic surgery. However, these classified benign nodules may continue to grow and ultimately may need to undergo surgery due to compressive symptoms. Although thyroid surgery has always been the mainstay of treatment for symptomatic nodular goiters, and is associated with excellent outcomes in experienced hands, thyroid surgery carries a low risk of complications that include recurrent or superior laryngeal nerve injury leading to voice changes, hypoparathyroidism, hypothyroidism with need for thyroid hormone supplementation, and unsightly scarring. Although many patients with thyroid cancers find these risks acceptable, these risks are sometimes less acceptable to patients with benign disease. In an era when the medical field is treating thyroid diseases less aggressively, there is a pressing need to identify approaches to treat indolent malignant disease less invasively.

Introduced in the early 2000s, ultrasound-guided percutaneous ablation of thyroid lesions has emerged as a potential alternative to surgery in patients with benign thyroid nodules. Of the myriad ablation methods, the most commonly used technique is radiofrequency ablation (RFA). An expanding body of evidence shows that radiofrequency ablation and other percutaneous interventions are effective treatments for benign solid thyroid nodules, toxic adenomas, and thyroid cysts resulting in overall volume reduction ranges of 40-70% with durable resolution of compressive and hyperthyroid symptoms. In addition, RFA has been used as an effective alternative treatment in the management of locally recurrent thyroid cancers in patients who are not good surgical candidates. Although these percutaneous techniques have been steadily.

gaining acceptance in Europe and Asia over the past 20 years, they have been slow to be adopted in the US. There remains a dearth of data regarding clinical experience in the United States and no randomized clinical trials have been performed evaluating RFA vs active surveillance for micropapillary carcinomas.

Inclusion Criteria:

• Indeterminate Bethesda III nodules that have been molecularly profiled benign with either Afirma Genomic Sequencing Classifier (GSC) or ThyroSeq v3 tests

Exclusion Criteria:

• cardiac arrthymias
• pregnancy

Adult patients (>/= 18 years) who have biopsy proven indeterminate thyroid nodules (Bethesda III only) that have been molecular profiled benign, who refuse to undergo or are not good candidates for surgical resection