Background: Fine-needle aspiration (FNA) is the most accurate tool to identify malignancy in solitary thyroid nodules. Although some recommend routinely repeating FNA for nodules that are initially read as benign, there is no consensus. We evaluated clinical relevancy and considered costs of routine follow-up FNA in nodules initially read as benign.
Methods: We reviewed the records of all 739 patients who underwent FNA of solitary thyroid nodules at our institution from 1988 to 2004. A total of 815 aspirations were required to obtain satisfactory specimens. According to their physicians practice, some patients had a "follow-up biopsy'' after an initially benign FNA reading as a matter of routine (Group I approach) or if their clinical status changed (Group II approach). The outcome information for at least 4 years after the initial FNA in these two groups was compared. In addition, hypothetical costs relating to both methods for deciding whether to do a follow-up FNA were considered.
Results: The initial FNA was benign in 576 (78%), suspicious for follicular neoplasms in 106 (14.4%), and malignant in 57 patients (7.7%). Follow-up FNA was performed in 292 patients with initially benign lesions, 235 in Group I approach and 57 in Group II approach. The FNA diagnosis according to Group I approach remained benign on follow-up biopsy in 96.2% (226/235), was altered to follicular neoplasm in 3% (7/235), and was suspicious for malignancy in 0.8% (2/235). When following Group II approach, the follow-up FNA was benign in 93% (53/57), undetermined in 1.7% (1/57), and showed follicular neoplasm in 5.3% (3/57). Combining Groups I and II methods, 5 of 292 patients had a malignant nodule on histological examination, a false-negative rate of 1.7% for the initial FNA, but without a difference in prevalence of thyroid malignancy between the groups. Cost-consequence analysis showed no benefit in routine follow-up FNA after initially benign FNA readings.
Conclusions: Routine follow-up FNA in patients whose initial FNA is benign has a low diagnostic upgrading value and is relatively costly. In patients whose initial FNA is benign, we recommend the FNA be repeated only if clinically suspicious signs or complaints develop.