Use and accuracy of fine-needle aspiration cytology in histologically proven thyroid carcinoma: an audit using a national nathology database.

BACKGROUND: Fine-needle aspiration cytology is recommended as the first and most decisive diagnostic step in the workup of patients with nodular thyroid disease.
METHODS: A retrospective analysis of all thyroid carcinomas diagnosed was conducted using the Netherlands Pathology Database PALGA, which covers all cytologic and histologic examinations in the Netherlands, with the aim of investigating nationwide whether fine-needle aspiration cytology of the thyroid (FNAC-t) actually had been used prior to surgery for thyroid carcinoma and if so, with what result.
RESULTS: FNAC-t was used in 591 of the 890 patients (66%) analyzed, with a total of 769 aspirations (a single FNAC-t in 459 patients, multiple FNAC-ts in 132 patients). The overall sensitivity rate was 57%; when restricting the FNAC-ts to the most recent one for each patient, the sensitivity rate rose to 70%. Sensitivity was lowest for follicular carcinoma (67%) and was highest for anaplastic and medullary carcinomas (89%). Limiting these calculations to aspirations from patients with tumors > 10 mm was found to have very little influence on these rates (FNAC rate: 71%; overall sensitivity rate: 58%).
CONCLUSIONS: If the application rate (66%) and sensitivity for the most recent aspiration (70%) were considered regardless of the tumor size, only 47% of the malignancies were detected by FNAC-t. When patients with tumors > 10 mm and all FNAC-ts in this group are considered, only 41% of thyroid carcinoma cases were detected cytologically. Contrary to common belief based on current guidelines for the workup of patients with nodular thyroid disease, the majority of thyroid carcinoma cases are not detected by FNAC-t.