Fine‐Needle Aspiration Cytology of Thyroid Gland: A Cytology/Histology Correlation Study in Northern Ireland

Abstract

Objectives: Fine needle aspiration cytology (FNAC) is a well-established preoperative investigation of thyroid nodules. British-Thyroid-Association (BTA) guidance recommends thyroid cytology reporting with “Thy” classification (Thy1 (non-diagnostic), Thy2 (benign), Thy3 (indeterminate), Thy4 (suspicious), Thy5 (malignant)). Our aim was to correlate the thyroid FNAC results with final histo-pathological diagnosis in patients undergoing thyroidectomy. Methods: Retrospective case-note analysis of 190 consecutive patients who underwent thyroid operations from 2009 to 2012. Most had ultrasound-guided-FNA (USgFNA) by an experienced radiologist. Patient demographics, FNAC results, ultrasound reports, and final histo-pathological diagnoses were analyzed. Results: Mean age was 50 (range 14-87). Male:Female was 1:5 (36:154). Sixty-one percent (115/190) had hemi-thyroidectomy. Thirty-nine percent (75/190) had total/completion thyroidectomy. Twenty-four percent (45/190) had diagnosis of thyroid cancer. Preoperative FNAC showed Thy1-9% (17), Thy2-16% (30), Thy3-55% (105), Thy4-8% (15), and Thy5-3% (5). No FNAC was carried out in 9% (18) (4 had surgery for refractory Graves, and 14 had surgery for massive retro-sternal-goiter). Postoperative histopathology results correlated correctly in 80% of Thy4 and Thy5 (4/5 with Thy5 and 12/14 with Thy4 had thyroid malignancy (9-PTC, 5-follicular, 2-anaplastic)). In the Thy3 category, 21% had thyroid cancer (11-PTC, 7-Follicular, 3-undifferentiated), 35% had multi-nodular goiter, and 25% had adenoma. Twenty-nine percent (5/17) of Thy1 and 3% (1/20) who had surgery for suspicious clinical/ultrasound features also had cancer. Conclusions: USgFNA offers a very sensitive and accurate method in detecting malignancy (>80% both in Thy5 and Thy4 and >29% in Thy3 lesions). Our study demonstrated >29% of patients with non-diagnostic FNAC (Thy1) with suspicious clinical or radiological features had thyroid malignancy, and we recommend diagnostic hemi-thyroidectomy in this subgroup.