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FNA may rule out malignancy in large thyroid nodules
Fine-needle aspiration can be a reliable test to rule out malignancy in thyroid nodules at least 4 cm when cancer prevalence and negative predictive value are known, according to study findings.
“Although the sensitivity and specificity of [fine-needle aspiration (FNA)] in large nodules is relatively low, the prevalence of cancer in these nodules at our center led to an excellent negative predictive value,” Roger Kulstad, MD, an endocrinologist at the Marshfield Clinic – Weston Center in Weston, Wisconsin, told Endocrine Today. “The false negative rate of FNA at our center was very low, especially if you exclude papillary microcarcinomas. However, it is important to remember the consequences of a false negative FNA in these patients. It is one thing to have a false negative FNA in a patient with a 1 cm tumor vs. a false negative FNA in a patient with a 4 cm tumor.”
Roger Kulstad
Kulstad evaluated 198 patients with large thyroid nodules ( 4 cm) who visited Marshfield Clinic from 2000 to 2010 to determine accuracy of fine-needle aspiration (FNA) in a clinical setting for detecting or ruling out malignancy in the nodules as well as desirability of using FNA to guide surgical decisions.
Sixty percent of participants (n = 119) had one nodule (uninodular group) and 40% (n = 79) had multiple nodules (multinodular group) with at least one 4 cm or larger. Cancer was identified in 23.8% of nodules after surgery, including 7.3% that were categorized as benign after FNA. Malignancies were identified in the nodule in all of the uninodular group and in the primary biopsied nodule in the multinodular group.
FNA resulted in about 80% sensitivity and specificity for all patients; positive predictive value was less than 60% and negative predictive value was 93%.
“It is important to remember that the negative predictive value reported in this study is based on the estimated prevalence of malignancy at our center,” Kulstad told Endocrine Today. “The prevalence of malignancy in large nodules may vary across centers and thus [negative predictive value] may be quite different elsewhere. I would encourage others to determine the prevalence rates of malignancy in large nodules at their own medical centers in order to calculate their own positive and negative predictive values.” – by Amber Cox
For more information:
Roger Kulstad, MD, can be reached at Marshfield Clinic – Weston Center, 3501 Cranberry Boulevard, Weston, WI 54476; email: kulstad.roger@marshfieldclinic.org.
Disclosure: Kulstad reports no relevant financial disclosures.