OBJECTIVE: Graves' disease (GD) is an autoimmune thyroid disorder characterized by hyperthyroidism. The incidence of thyroid cancer in patients with GD varies from 0.15% to 15%. There is conflicting evidence on the role of thyroid nodules as a risk factor for thyroid cancer in patients with GD.DESIGN: Three electronic databases (PubMed, Cochrane Library, Scopus) as well as grey literature sources were searched, from inception until 25 February 2019, for observational studies about the prevalence of thyroid cancer in patients with GD.PATIENTS: Clinical and ultrasonographic examination was necessary preoperatively for all patients to be classified depending on the presence/absence of thyroid nodules.MEASUREMENTS: Primary outcome was the incidence of thyroid cancer. The latter was determined after total or near-total thyroidectomy by the histopathologic report. Statistical analysis was performed with revman 5.3 software.RESULTS: The systematic review and meta-analysis included 7 studies with 2582 patients overall. The prevalence of any thyroid cancer was 11.5%. The presence of at least one thyroid nodule in patients with GD was associated with higher risk for thyroid cancer (odds ratio [OR] 5.3, 95% confidence interval [CI] 2.4-11.6, I 83%). A subgroup analysis showed no difference in thyroid cancer risk in patients with GD according to the number of nodules (solitary versus multiple) (OR 1.4, 95% CI 0.9-2.3, I 0%).CONCLUSIONS: The presence of thyroid nodules is positively associated with the prevalence of thyroid cancer in surgically treated patients with GD. However, further prospective research is needed as the heterogeneity among the studies is high.