Follicular variant of papillary thyroid carcinoma: comparison of ultrasound-guided core needle biopsy and ultrasound-guided fine needle aspiration in a multicentre study.

Abstract

Pre-operative diagnosis of the follicular variant of papillary thyroid carcinoma (FVPTC) by ultrasound-guided fine needle aspiration (US-FNA) remains a challenge. The goal of this study was to investigate whether ultrasound-guided core needle biopsy (US-CNB) is superior to US-FNA in refining the surgical indications for the treatment of FVPTC. This retrospective study enrolled 212 patients with 218 FVPTCs who were surgically confirmed at three university hospitals from January 2008 through December 2014. All patients underwent both or either US-FNA or US-CNB. FNA and CNB results were divided into identified surgical candidates or not based on the Bethesda system. Relevant clinical information and the rate of surgical candidates were compared between US-FNA and US-CNB groups. Among 218 thyroid nodules, US-FNA was performed for 200 nodules and US-CNB for 51 nodules. Thirty-three nodules underwent both US-FNA and US-CNB. The rates of surgical candidates identified by US-FNA and US-CNB were 61·5% and 86·3%, respectively (P = 0·001). The rates of surgical candidates identified by repeat US-FNA and initial US-FNA with subsequent US-CNB were 53·9% and 78·8%, respectively (P = 0·042). A precise diagnosis of FVPTC was made in 1% of the patients in the US-FNA group and in 29·4% of the patients in the US-CNB group. The predominant US findings of FVPTCs included solid tumours (89·4%), wider-than-tall shape (82·6%), no calcifications (51·3%), hypoechogenicity (46·3%) and indeterminate diagnosis on US (50·5%). In patients with FVPTC, US-CNB is a superior indicator for surgery compared to US-FNA. If a FVPTC is suspected but is initially indeterminate at FNA cytology, subsequent US-CNB should be considered instead of repeat US-FNA.