Diagnostic management of solitary thyroid nodules.

The study attempts to assess the accuracy of radionuclide scan, ultrasonography and fine-needle aspiration biopsy as diagnostic tools in distinguishing malignant from benign nodular thyroid lesions in Singapore. The medical case records of 537 patients referred to the Department of Nuclear Medicine were analysed. 94% of the solitary thyroid nodules delineated on scintiscan were "cold". The incidence of malignancy in solitary "cold" thyroid nodules was 8%, and that in multinodular goitres was 2.3%. The sensitivity of both radionuclide scan and ultrasonography in detecting cancer was 100%, but the specificity was disappointingly low, i.e. 3.6% for radionuclide scan and 21% for ultrasonography. The sensitivity for fine-needle aspiration biopsy was 85%, and the specificity 96%. Fine-needle aspiration cytology is indisputable as an accurate diagnostic tool in differentiating malignant from benign thyroid lesions, and should be the first test to be used in the diagnostic workup of nodular thyroid disease. However, both radionuclide scan and ultrasonography remain crucial in the subsequent management of patients with thyroidectomy done for thyroid cancer. The other major roles are in the management of thyroiditis, thyrotoxicosis and confirmation of ectopic thyroid tissue.