Background: Recent American Thyroid Association guidelines call for thyroidectomy or 131I (Recommendation 31) in managing hyperthyroidism due to toxic nodular goiter (TNG). Concern for concomitant malignancy favors surgery. A 3 % thyroid cancer incidence in TNG patients has been reported, yet recent studies suggest this rate is underestimated. This multi-institutional study examined cancer incidence in TNG patients referred to surgery. Methods: Patients referred for thyroidectomy at three tertiary-care institutions were included (2002-2011). Patients with concurrent indeterminate or malignant diagnosis by fine-needle aspiration (FNA) were excluded. Cancer incidence in TNG patients was determined. Fisher's exact and chi-square tests and nonparametric t tests were used. Results: Among 2,551 surgically treated patients, 164 had TNG (6.4 %). Median age at presentation was 49.7 years, and 86 % were female. Overall cancer incidence was 18.3 % (30 of 164), and rates were not significantly different between institutions. A significantly greater cancer rate was noted in toxic multinodular goiter versus single toxic nodule patients (21 vs. 4.5 %, P < 0.05). Mean tumor size was 0.71 cm (range 0.1-1.5 cm; 23 % ≥1 cm). Most patients underwent total or near-total thyroidectomy. There were no significant differences in tumor sizes among institutions (P > 0.05). No significant cancer association was noted with age, preoperative dominant nodule size, lymphocytic thyroiditis or preoperative FNA (P > 0.05). Conclusions: These data demonstrate a higher than expected incidental cancer rate in TNG patients compared to historical reports (18.3 vs. 3 %). This higher cancer incidence may alter the risk/benefit analysis regarding TNG treatment. This information should be provided to TNG patients before decision making regarding treatment.
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