Thyroid carcinoma in Graves' disease: A meta-analysis.

BACKGROUND: The incidence of thyroid carcinoma is increasing worldwide. Graves' disease is the most common hyperthyroid disease. Studies have suggested an increased risk of thyroid malignancy in Graves' disease: there has not yet been a meta-analysis to allow quantitative comparison. The purpose of this study was to determine the risk of thyroid carcinoma in Graves' disease, and to gather information on the histological subtypes of carcinoma and the co-existence of thyroid nodules.

METHODS: Several databases and article reference lists were searched. Inclusion criteria included appropriate diagnostic criteria for thyroid conditions and a diagnoses of carcinoma based on histology.

RESULTS: 33 studies were selected, all reporting on surgically-resected specimens. The event rate of thyroid carcinoma in Graves' disease was 0.07 (95% CI 0.04 to 0.12). There was no data to allow comparison with patients without hyperthyroid diseases. There was no increase in the odds of developing carcinoma in Graves' disease compared to toxic multinodular goitre and toxic uninodular goitre. 88% of thyroid carcinomas in Graves' disease were papillary, with solitary papillary micro-carcinoma (diameter 10 mm or less) comprising 23% of all detected thyroid carcinomas. Patients with Graves' disease and co-existing thyroid nodules were almost 5 times more likely to be diagnosed with thyroid carcinoma than those without nodules.

CONCLUSION: Thyroid malignancy in Graves' disease requiring surgical treatment should be considered as likely as in other hyperthyroid diseases needing surgical treatment. Clinicians should consider screening selected patients with Graves' disease for nodules whilst being aware of potentially over-diagnosing papillary micro-carcinoma.