Usefulness of repeated fine-needle cytology in the follow-up of non-operated thyroid nodules

OBJECTIVE: The usefulness of repeated fine-needle cytology (FNC) in thyroid nodules with benign cytology remains unknown. We analyzed the relevance of repeated FNC to detect suspicious or malignant (S/M) cytologies and carcinomas. DESIGN: A retrospective study (1983-2004) was conducted in our endocrinology department. METHODS: We reviewed the reports of 895 adequate FNC performed in 298 patients (298 nodules) during a mean follow-up of 5 years. We compared the nodules with at least one suspicious or malignant FNC (S/M nodules) with nodules with repeatedly benign (RB) FNC (RB nodules). RESULTS: Among the nodules with initial benign cytology, we found 35 nodules with one or more later suspicious or malignant results. The interval between the first FNC and the first S/M FNC was 2.9 years. The probability for a nodule to have a repeated benign FNC decreases with time and with the number of FNC. We did not find any clinical or ultrasonographic characteristics related to an S/M cytology. Seven cancers were detected by the second or the third FNC with S/M results. The proportion of cancers among S/M nodules was similar when S/M cytology appears during the first, the second, or the third FNC. CONCLUSIONS: We suggest to repeat FNC up to three adequate samples in the follow-up of thyroid nodules so as not to miss the presence of malignant neoplasm.