Diagnosis and treatment of cystic disease of the thyroid by aspiration.

One hundred forty-one cases of euthyroid solitary "cold" and "uniform" nodules, each of which contained at least 3 ml of fluid obtained on aspiration, are presented. Sixty-three patients had complete disappearance of swelling after one aspiration. Seventy-eight patients were selected for surgery on the basis of cytologic findings of malignancy in the aspirated fluid (one patient), on the basis of recurrent cyst formation after one aspiration (17 patients; in these cases the incidence of malignancy was similar to that in solid, cold nodules), and on the basis of palpable tissue after aspiration that indicated a partially cystic lesion (60 patients). Surgicopathologic findings revealed six malignant lesions; all of these nodules were more than 3 cm in diameter. In percentage, 6.6% of the partially cystic and 2.5% of the purely cystic nodules were malignant. The color of the aspirated fluid did not add to the discriminant value of the aspirate. The identification of malignant conditions in thyroid cysts was handicapped by the yield of acellular material in three of five cases of malignant disease and in more than 50% of benign lesions. However, the study suggests that aspiration biopsy of cystic thyroid nodules when used in association with the above clinical criteria is a useful technique of selecting patients for operation and, by itself, is a safe and reliable means of treating the disorder.