Risk of Malignancy in Thyroid Nodules with Non-Diagnostic Fine-Needle Aspiration: A Retrospective Cohort Study

Abstract

Background: Fine-needle aspiration (FNA) of thyroid nodules is commonly performed, and despite the use of ultrasound (US) guidance, the rate of non-diagnostic FNAs is still significant. The risk of malignancy of thyroid nodules with a non-diagnostic FNA is not clearly defined. However, most studies exclude the majority of patients without a repeat biopsy or surgery, thus increasing the likelihood of selection bias. The aims of this study were to determine the malignancy risk in nodules with an initial non-diagnostic FNA, and to identify the factors associated with malignancy. Methods: This was a retrospective cohort study of patients with thyroid nodules who underwent US-guided FNA between 2004 and 2010 and had a non-diagnostic result. Patients were followed until confirmatory diagnosis of the nature of the nodule was made. The outcome of malignant or benign disease was based on one of the following: (i) final surgical pathology following thyroidectomy; (ii) repeat biopsy; (iii) clinically, based on repeat ultrasound performed at least three years following biopsy; or (iv) report of thyroid status for patients without follow-up visits contacted by mail. Results: There were 699 nodules from 665 patients included. The mean age was 59 -15 years, and 71.7% were women. There was complete follow-up of 495 nodules. After a median follow-up of 2.7 years, thyroid cancer was found in 15 nodules. The prevalence of malignancy was 3% (15/495). The presence of nodular calcifications was the strongest predictor of thyroid malignancy (odds ratio 5.03 [confidence interval 1.8-14.7]). Initial nodule size was inversely associated with malignancy (odds ratio 0.55 [confidence interval 0.28-0.93]). However, the 193 patients without follow-up had smaller nodules compared with those included in the analysis. None of the patients with repeatedly non-diagnostic results were diagnosed with thyroid cancer at follow-up. Conclusion: The prevalence of thyroid cancer in nodules with non-diagnostic results is lower than the malignancy rate in thyroid nodules in general, but not negligible. They should be followed as per guidelines with heightened suspicion for nodules containing calcifications. Nodules with repeatedly non-diagnostic FNA results especially in the absence of calcifications have a low risk of malignancy and may be observed.

The Role of Core Needle Biopsy for Thyroid Nodules with Initially Indeterminate Results on Previous Fine-Needle Aspiration: A Systematic Review and Meta-Analysis

“…Repeat FNA also provides definitive categorization of indeterminate nodules. 38 Fourth, the prevalence of malignancy in patients with nondiagnostic/indeterminate thyroid nodules and the mortality of thyroid cancer remains low. Therefore, the clinical impact of the observed higher conclusive results of CNB compared with repeat FNA could be controversial.…”

Clinical and Ultrasound Thyroid Nodule Characteristics and Their Association with Cytological and Histopathological Outcomes: A Retrospective Multicenter Study in High-Resolution Thyroid Nodule Clinics

“…Similarly, these high-resolution nodule clinics have been shown not only to be cost-effective [29] but also to reduce the delay in diagnosis and to improve patients' satisfaction [9,29]. Along this line, our nondiagnostic FNA (Bethesda I) rate (4.3%) was lower than the usually reported rate of 8%-20% in several studies [30]. Previously, Díaz-Soto et al, in a single-center HR-TNC study, found a similar percentage of inadequate samples for cytology (4%) [29].…”

Screening for thyroid diseases among students of applied medical sciences at King Abdulaziz University, Saudi Arabia

“…The diagnosis must be performed with respect to the standard procedure of the recommended guidelines, although the incidence of thyroid cancers remains low. 12 Results displayed only 3 (8.8%) of the lesions that had sonographic features. It suggested a possibility of malignancy; therefore, FNA was not performed in all the 3 cases.…”