RESUMO
OBJECTIVE: To evaluate sensitivity of fine needle aspiration cytology in diagnosing malignancy in histologically proven thyroid cancers. STUDY DESIGN: We analyzed the results of 335 smears from clinically significant and histologically proven primary thyroid cancers obtained from 9,115 aspirates, taking into account the pathologist's experience. RESULTS: The sensitivity for diagnosing thyroid malignancy in general was 88.0% (range, 82.6-97.2% from less to more experienced pathologist, respectively). It was higher for papillary (mean, 91.9%) and medullary (mean, 95.4%) carcinomas than for follicular cancer (mean, 50.0%). Biopsy showed thyroid cancer in 27.4% suspicious (range, 22.9-33.3%), 4.4% indeterminate (range, 1.9-6.6%) and 4.1% negative (range, 0-6.6%) smears. CONCLUSION: The more experienced the pathologist, the higher the sensitivity rate for recognizing thyroid cancer in general and by histologic type on aspirates despite some limitations of the method in identifying follicular carcinoma. We recommend thyroidectomy for patients with positive smears and follow-up for patients with benign, indeterminate and suspicious cytology, provided that the cytologic specimens were reviewed by an experienced pathologist.