Purpose: The incidence and aggressiveness of thyroid cancer associated with hyperthyroidism remains a subject of much controversy. The aim of this study was to analyze the frequency of coexisting hyperthyroidism and thyroid cancer, and to determine whether cancer becomes more aggressive with different forms of hyperthyroidism.
Methods: We retrospectively studied 2,449 patients assessed for hyperthyroidism between 1985 and 2001. All patients with a "cold" nodule on scintigraphy, such as those with Graves' disease and a concomitant solid nodule, underwent fine-needle aspiration biopsy (FNAB). Criteria for surgery were cytological findings indicative of malignancy, goiter with signs of tracheal or esophageal compression, side effects of antithyroid drug therapy, or Graves' disease with multiple relapses after therapy withdrawal or responsiveness to antithyroid drugs.
Results: Thyroid cancer was diagnosed more frequently in patients with Graves' disease (6.5%) than in those with uninodular toxic goiter (UTG) (4.4%) or multinodular toxic goiter (MTG) (3.9%). Lymph node involvement was found in 56% of the patients with Graves' disease, in 23% of those with MTG, and in none of those with UTG. Distant metastases were found in one patient with Graves' disease.
Conclusions: Cancers associated with Graves' disease seems to be more aggressive than those associated with MTG or UTG. Thus, we suggest that patients with Graves' disease be carefully monitored for the detection of thyroid nodules. Ultrasonography seems to be the best modality to detect such nodules.