Thyroid cancer in hyperthyroidism: incidence rates and value of ultrasound-guided fine-needle aspiration biopsy in this patient group.

Three hundred and thirty-three hyperthyroidism cases were retrospectively investigated to provide information about the association between hyperthyroidism and thyroid cancer. There were 112 cases of toxic multinodular goiter (TMNG), 77 cases of toxic nodular goiter (TNG) and 144 cases of Graves' disease (GD). All nodules detected in GD patients, all nodules greater than 1 cm diameter in nodular goiter patients, nodules 5-10 mm size diameter if they had calcification were fine-needle biopsied (FNAB) under ultrasound guidance (US-guided), and a total of 612 such biopsies were performed. The biopsy samples were cytologically assessed as benign (no.=552; 90.2%), suspicious (no.=6; 1.1%), malignant (no.=13; 2.1%), or inadequate for diagnosis (no.=41; 6.7%). All patients with a biopsy diagnosis of malignant or suspicious nodules underwent surgery. Histological examination confirmed the diagnosis of thyroid cancer in all 13 (2.1%) patients with malignant FNAB findings. Papillary thyroid carcinoma (PTC) was identified in 2 patients with TMNG (%1.8), 5 with TNG (%6.5) and 5 with GD (%3.5). Metastatic follicular thyroid carcinoma (FTC) was identified in a patient with TNG. Thyroid malignancy (micro- or macrocarcinoma) was diagnosed pre-operatively in all 13 cases by US-guided FNAB. Thyroid cancer was diagnosed in 6 (5.5%) of the 109 nodules detected in the TNG group, 2 (0.44%) of the 452 nodules detected in the TMNG group, and 5 (9.8%) of the 51 nodules detected in the GD group. Two (2.6%) of the 77 functioning nodules in the TNG patients were malignant, but none of the 402 functioning nodules in the TMNG patients was malignant. In patients with hyperthyroidism, US-guided FNAB is useful for detecting thyroid cancer in nodules greater than 5 mm diameter before radioiodine therapy or surgery.