Does Tumor Size Influence the Diagnostic Accuracy of Ultrasound-Guided Fine-Needle Aspiration Cytology for Thyroid Nodules?

Abstract

Background. Fine-needle aspiration cytology (FNAC) is diagnostic standard for thyroid nodules. However, the influence of size on FNAC accuracy remains unclear especially in too small or too large thyroid nodules. The objective of this retrospective cohort study was to investigate the effect of nodule size on FNAC accuracy. Methods. All consecutive patients who underwent thyroidectomy for nodules in 2010 were enrolled. FNAC results (according to the Bethesda system) were compared to pathological diagnosis. The nodules were categorized into groups A–E on the basis of maximal diameter on ultrasound (≤0.5, >0.5–1, >1-2, >2–4, and >4 cm, resp.). Results. There were 502 cases with 690 nodules. Overall FNAC sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 95.4%, 98.2%, 99.4%, 86.4%, and 96.0%, respectively. False-negative rates (FNRs) of groups A–E were 3.2%, 5.1%, 1.3%, 13.3%, and 50%, respectively. Accuracy rates of groups A–E were 96.8%, 94.8%, 99%, 94.7%, and 87.5%, respectively. Conclusion. Although accuracy rates of FNAC in thyroid nodules smaller than 0.5 cm are comparable to the other group, thyroid nodules larger than 4 cm with benign cytology carry a higher risk of malignancy, which suggest that those should be considered for intensive follow-up or repeated biopsy.

The influence of thyroid nodule size on the diagnostic efficacy and accuracy of ultrasound guided fine‐needle aspiration cytology

“…Authors concluded that the large nodule size should not be accepted as an indication for surgery alone. Our results were consistent with studies which suggested decreased sensitivity and increased false‐negative rate of FNAC in large nodules . The present study supports that the cancerous focus may be missed during the FNAC procedure in large nodules despite multiple aspirations.…”

“…Previously, Pinchot et al reported that the predictive value of FNAC was lower for the nodules greater than 40 mm and recommended diagnostic surgery for large thyroid nodules . In a recent study, Koo et al observed that the sensitivity of FNAC was lower in nodules greater than 40 mm when compared to smaller ones, whereas specificity was high in all groups of nodule size . Authors suggested that intensive follow‐up and repeat biopsies should be considered for large nodules.…”

“…Although, FNAC is the gold standard for differential diagnosis of thyroid nodules, a controversy exists regarding its utility on very small (<10 mm) and large (>30‐40 mm) nodules . A number of previous studies reported that false‐negative cytology results were frequent in larger nodules . Therefore, surgery was recommended in the management of large thyroid nodules .…”

False negative rate of fine‐needle aspiration in thyroid nodules: impact of nodule size and ultrasound pattern

“…There have been many conflicting reports in terms of false negative rate and nodule size in overall thyroid nodules . Although the reason for the conflicting results among the studies is not clear, it may be related to the proportion of FTC among malignant tumors and the size distribution of PTC in the study population.…”

“…Whether the high false negative rate in large thyroid nodules is real is still a matter of controversy; several studies have reported that large nodules were not associated with an increased risk of false negative FNA results . However, other studies have demonstrated that large thyroid nodules showed higher false negative rate than small nodules and that large nodules with benign cytology carry a higher risk of malignancy …”