Toxic nodular goiter and thyroid cancer: Is hyperthyroidism protective against thyroid cancer?

Background: The suppressive effect of the increase in thyroid hormone in patients with toxic nodular goiter is thought to protect the extranodular thyroid tissue from thyroid malignancy. In this study, we aimed to evaluate the prevalence and features of thyroid cancer in patients with toxic nodular goiter who underwent thyroidectomy. Methods: Medical data of patients who had solitary toxic or nontoxic nodules and underwent total thyroidectomy were reviewed retrospectively. We reviewed the clinical, laboratory, and histopathologic features of patients with toxic nodular goiter and nontoxic solitary nodules. Results: There were 73 patients with toxic nodular goiter and 366 patients with nontoxic solitary nodules. Median age was greater in the toxic nodular goiter compared with nontoxic solitary nodules patients (50 years; range: 18-73 vs 42 years; range: 18-83, P < .001). Median nodule diameters were 40.9 mm (range: 11.0-98.0) and 23.3 mm (range: 4.9-99.0) in patients with toxic nodular goiter and nontoxic solitary nodules, respectively (P < .001). Histopathologic examination revealed thyroid cancer in 14 patients (19%) with toxic nodular goiter and 132 (36.1%) patients with nontoxic solitary nodules (P = .008). Median tumor diameters were 6 mm (range: 1-50) in toxic nodular goiter and 14 mm (range: 1-80) in nontoxic solitary nodules (P = .150). The malignant nodule was the hyperfunctioning nodule in 7 patients with toxic nodular goiter; 4 were follicular and 3 were papillary thyroid cancer. The other 7 malignant foci were located in the suppressed contralateral lobe, and all were papillary microcarcinomas. The incidence of thyroid cancer outside the main nodule was similar in 2 groups (P = .934). Conclusion: Thyroid cancer in patients operated for toxic nodular goiter was 19%, which is not as rare as previously thought. A careful histopathologic examination of both the hyperfunctioning nodule and the extranodular thyroid tissue might help to disclose an unexpected tumor foci when thyroidectomy is performed in patients with toxic nodular goiter. (C) 2019 Elsevier Inc. All rights reserved.