Fine-needle aspiration (FNA) has high sensitivity and specificity in distinguishing benign from malignant thyroid lesions. However, in 5-20% of the cases belonging to the indeterminate cytology categories (follicular neoplasms and atypia of undetermined significance) it is not possible to discriminate between benign and malignant tumours. As a consequence of this limitation, patients with such diagnoses have to be submitted to diagnostic rather than to curative thyroid surgery.
