RESUMO
BACKGROUND: Thyroid ultrasonography (US) is the most sensitive method for detecting thyroid nodules, and US-guided aspiration biopsy is the most accurate diagnostic procedure for thyroid nodules. We performed this retrospective study to establish the prevalence of thyroid nodules in Graves' disease and patients with Hashimoto's thyroiditis at the time of their initial visit. METHODS: We performed thyroid US as routine screening in 1652 patients with Graves' disease and 2036 Hashimoto's thyroiditis and performed US-guided fine-needle aspiration biopsy when the diameter of a nodule >1 cm or a nodule was suspected of being malignant. RESULTS: The prevalence of papillary carcinoma in the patients with Hashimoto's thyroiditis was higher than in the patients with Graves' disease (1.77% vs. 0.97%), and two patients with Hashimoto's thyroiditis (0.098%) were found to have malignant lymphoma. Adenomatous lesions were observed more frequently in the patients with Hashimoto's thyroiditis than in the patients with Graves' disease. The prevalence of adenomatous lesions increased in an age-dependent manner in both the patients with Graves' disease and those with Hashimoto disease; and adenomatous lesions were more frequent in younger patients with Hashimoto' s thyroiditis than in those with Graves' disease. CONCLUSIONS: The prevalence of both thyroid papillary cancer and adenomatous lesions was greater in the patients with Hashimoto's thyroiditis than in those with Graves' disease; and adenomatous lesions were more frequent in younger patients with Hashimoto's thyroiditis. We recommend performing US at the time of the initial visit in patients with autoimmune thyroid disease, who have a high prevalence of thyroid papillary carcinoma, to detect malignant thyroid tumors and adenomatous lesions.