Risk Factors for Malignancy of Thyroid Nodules Initially Identified as Follicular Neoplasia by Fine-Needle Aspiration: Results of a Prospective Study of One Hundred Twenty Patients

Abstract

Indeterminate or suspicious findings on fine-needle aspiration (FNA) of nodular thyroid disease (i.e., findings that neither give immediate indication for surgery nor lead to clear-cut conservative management) have been the key diagnostic problem in thyroid cytology for which the inability to differentiate cytologically benign from malignant follicular growth has been one reason. The aim of this cohort study of 120 consecutive (103 females, 17 males) patients with palpable nodular thyroid disease diagnosed as follicular neoplasia (FN) by FNA (defined by the triad of high numbers of follicular cells, microfollicular arrangement, and scanty or absent colloid) was to identify patients at high risk for malignancy based on the prospective evaluation of clinical features and to characterize the histologic entities of FN. Based on a 100% surgery rate we found an 18% malignancy rate (12 papillary carcinomas, 9 follicular carcinomas). Previously suggested factors with elevated risk for malignancy such as extremes of age, male gender, and large nodule size were not associated with increased risk as were cold nodules by ^99mTc-scintigraphy (relative risk: 1.2, 95% confidence interval [CI] 0.4-3.3). However, hard lesions to palpation (relative risk 2.6, 95% CI: 1.2-5.6), solitary (relative risk: 2.6, 95% CI: 1.7-4.0), and hypoechoic FNs (relative risk: 3.4, 95% CI: 2.0-5.7) by ultrasound showed elevated risks of malignancy. In summary, suspicious palpation or ultrasound results may help to define a subgroup of patients with elevated risk of malignancy when FNA indicates the diagnosis of follicular neoplasm of the thyroid.