Reevaluation of needle aspiration cytology in detection of thyroid cancer.

From July, 1978, to August, 1980, 379 patients with thyroid disease were assessed clinically and underwent scintiscanning and needle aspiration cytology. One hundred fifty-three patients were selected for operation, there were 138 solid lesions and 15 cystic lesions. Selection criteria included clinical factors as well as cytology results. There was a cancer rate of 33% and a neoplasia rate of 92%. In the solid lesions there was a 36% incidence of cancer, whereas the incidence was 27% in cystic lesions. There was a false positive rate of 1%. A false negative rate could be viewed in various ways. Twenty-four cancers were missed in benign cytology for an incidence of 25%; however if one excluded the cytologic abnormal group, as some authors do, labeling them as potential malignancies, false negative results occurred in the cytologic benign cases for a rate of 4% for the entire group. If noncystic benign lesions alone were considered, the false negative rate would be 1%. False negative reporting arises predominantly from the inability to differentiate follicular adenoma from adenocarcinoma in cytology. Other factors such as geographic miss cystic disease also play a role. If one is to avoid underdiagnosis and undertreatment of thyroid cancer, one should consider cellular aspirates as potentially malignant and subject to surgical excision. Needle aspiration cytology has an unassailable role in the management of the patient with thyroid disease but requires interpretation in the light of clinical and scintiscanning results.