Reliability of aspiration biopsy in thyroid nodes: study of 2190 operated patients.

The cytologic finding was negative in 1841 patients; accurate in 1763 (95.8%). Suspicious cytology proved malignant in 82 of 252 patients (32.5%). Positive cytology was accurate in 88 out of 97 cases (90.7%). In 1942 benign goiters, cytology was accurate in 90.8% of patients, false suspicious in 8.7% and false positive in 0.5%; the highest percentage of misdiagnosis was in adenomas (15.8%) and thyroiditis (19.0). In 248 malignant goiters, cytology was accurate in 35.5% of patients, suspicious in 33.1%, and false negative in 31.4%. False-negative cytology was found in 44% of follicular cancers, 22.2% of papillary and medullary, and 12.9% anaplastic. The most frequent false-negative cytologic diagnosis was the adenomatous goiter. The accuracy of cytology was statistically higher in papillary cancers than in follicular (77.8% vs 56.0%), in undifferentiated tumors than in differentiated (83.7% vs 65.0%), and in adenomatous nontoxic goiters than in adenomas, thyroiditis and toxic goiters (80.3% vs 42.7%), 20.1% and 13.4%). Positive preoperative fine needle aspiration biopsy cytology is a worthwhile and reliable finding; it fails in less than 10% of patients. Negative cytology, however, does not exclude malignancy in thyroid nodes; it is false negative in more than 30% of cancers.