The natural history of the benign thyroid nodule: what is the appropriate follow-up strategy?

Background: Long-term monitoring of benign thyroid nodules is not addressed in the present American Thyroid Association guidelines. The objective of this study was to determine the appropriate nature and length of follow-up for patients with a benign thyroid nodule.

Study Design: A retrospective review was performed of all patients referred to single endocrine surgeon for evaluation of thyroid nodules between 2006 and 2012. The review included 263 patients who had benign fine needle aspiration (FNA) cytology and either underwent thyroidectomy or had at least a 1-year follow-up ultrasound. Main outcomes measures were repeat FNA and pathology results.

Results: There were 231 women and 32 men. Forty-eight patients underwent immediate thyroidectomy, with pathology showing 2 papillary thyroid cancers (PTC), and 215 patients were followed with annual ultrasounds. During follow-up, 89 (41.3%) nodules underwent repeat FNA after initial biopsy. The repeat FNA cytology showed 91% benign, 7% follicular neoplasm, and 2% PTC. During follow-up, 81 (37.6%) patients underwent thyroidectomy after 3.3±2.8 years. Reasons for surgery included development of symptoms in 58 (71.6%), a non-benign repeat FNA in 8 (9.8%), or patient preference in 15 (18.5%). Surgical pathology identified 70 (86.4%) benign, 7 (8.6%) PTC, 3 (4%) follicular thyroid cancers, and 1 (1.2%) lymphoma. Median time from initial FNA to thyroidectomy in patients who had malignancy was 4.3 years. The maximum initial nodule size and average increase in nodule size did not differ between benign and malignant nodules (p=0.54 and p=0.75, respectively).

Conclusions: Significant numbers of benign thyroid nodules enlarge more than 5 mm over 3 years, triggering repeat FNA or thyroidectomy. Larger diameter nodules and more rapidly growing nodules were not predictive of malignancy. The practice of annually obtaining ultrasound for benign thyroid nodules should be discouraged.