Background: Application of fine needle cytology (FNC) is important in the preoperative assessment of thyroid lesions. The method is rapid, minimally invasive and cost effective. The aim of this study was to evaluate the role of fine needle cytology at The Norwegian Radium Hospital in the management of thyroid nodules.
Material and methods: Data on FNC and comparable histology results were retrieved from the pathology database during the 5-year-period 1998 through 2003. 1770 FNC samples and corresponding histology results from 443 lesions were compared. Reviews of cytological slides were done in 39 discrepant cases and quality assessment parameters calculated.
Results: High complete sensitivity (77.5%) and specificity (90.1%) were found. The false positive rate was 1.2% and the false negative rate 23.7%. Inadequate FNCs were particularly seen in submitted specimens. A review of the discrepant cases showed that the main cause of false negative samples was sampling error. Micropapillary carcinoma was the predominant tumour type with false negative FNC. Eleven malignancies were diagnosed in repeat FNC specimens.
Interpretation: FNC is a highly reliable test to assess whether a thyroid nodule is benign or malignant. Diagnostic pitfalls are mainly due to inability to procure the diagnostic material.