Fine-needle aspiration of thyroid nodules in radiation-exposed patients.

Abstract

External radiation used to treat benign conditions in the head and neck area results in an increased risk of thyroid cancer in exposed individuals. Fine-needle aspiration (FNA) biopsy is the standard procedure used to evaluate suspicious thyroid nodules. Its accuracy has been extensively studied, but little is known about FNA in irradiated patients. We analyzed the FNA experience of 136 irradiated subjects. Fifty-two had surgery enabling a comparison of the histologic diagnosis with the FNA results. In these 52 patients with a total of 53 FNAs, 20 were reported as benign, 14 as follicular neoplasms, 6 as papillary cancer, and 13 as inadequate samples. Seven malignant nodules were aspirated; 4 were reported as papillary cancer, 1 was reported as benign and 2 had inadequate specimens. An additional 11 patients had thyroid cancer in foci that were not subjected to FNA. For the nodules that were aspirated, and considering an FNA report of follicular neoplasm as a false-positive when a follicular adenoma or a colloid nodule was found at surgery, the calculated sensitivity was 80%, specificity 54%, positive predictive value 20%, and negative predictive value 95%. Of the 14 follicular neoplasm FNA diagnoses, 10 were colloid nodules (71%), and 4 only were follicular adenomas. We conclude that the sensitivity of FNA in irradiated patients is similar to what is reported for the general population. However, smaller malignant nodules are common and are not diagnosed by the FNA. Also, the FNA diagnosis of follicular neoplasm is often inaccurate and inadequate aspirations are frequent in this patient group.