Benign fine-needle aspiration cytology of thyroid nodule: to repeat or not to repeat?

Fine-needle aspiration cytology (FNAC) is the gold standard for evaluating thyroid nodules. It has a sensitivity rate of about 95%, i.e. false negative results represent up to 5% of cases. The value of repeated FNAC during follow-up is still controversial.

To evaluate the usefulness of repeating the FNAC for initially benign nodules.

All 5017 patients who underwent FNAC of the thyroid nodule in years 1991-2008 were retrospectively evaluated.

Repeated FNAC was performed in 574 nodules with initially benign results. The number of repetitions varied from one to six. Repeatedly benign results were found in 498 cases, and malignant/suspicious results with initially benign cytology were found in 76 nodules (13.2%). Carcinoma was present in 13 out of the 58 surgically treated malignant/suspicious results of initially benign cytology.

A change from a benign FNAC result to a malignant/suspicious one was present in more than 13% of the patients with initially benign cytology; malignancy has been recognised on the basis of repeated FNAC in 2.3% patients. In the majority of cases, the repetition corrected wrong cytological interpretation of results other than colloidal goitre, especially Hashimoto's thyroiditis and regressive changes. We believe that repeating FNAC in patients with benign cytology in about a 1-year horizon can reduce the rate of undiagnosed tumours.