29. Audit of fine needle aspiration cytology assessment of thyroid nodules

Abstract

Fine-needle aspiration (FNA) is one of the first line investigations used to triage patients with suspected thyroid pathology. The introduction of the Bethesda Classification System for reporting thyroid cytopathology in 2007 aimed to create universal standards which would contribute to the most appropriate patient management. We audited our experience with this system for the calendar year 2010. We examined 495 thyroid FNA samples from 355 patients. Of the 495 FNAs, 17.4% were category 1 non-diagnostic, 70.7% were category 2 benign, 4.4% were category 3 atypical, 4% were category 4 suspicious for follicular neoplasm, 0.4% were category 5 suspicious for carcinoma and 3% were malignant. All category 5 and 6 cases were found to be malignant at surgery. There was limited follow-up for categories 3 and 4. For category 3, 88% were benign at surgery or category 2 at follow up FNA, with 12% being upgraded to category 4 at repeat FNA (no follow up surgical data available). For the 20 category 4 cases definitive surgical follow-up was only available in eight cases, with five (63%) being benign and three (37%) representing follicular carcinoma. Given that we review most follicular carcinomas resected elsewhere but biopsied in our unit, we suspect that the true rate of malignancy for category 4 aspirates in our unit is 15%.