[Fine needle aspiration cytology of 637 thyroid nodules].

Fine needle aspiration cytology was performed in the preoperative evaluation of 637 thyroid nodules. Cytological findings in benign and malignant tumor were classified and compared. In 514 cases in which cells were sampled, accuracy rate, false negative rate and false positive rate of cytology was 88.0, 7.0 and 4.1%, respectively. The corresponding figures of clinical diagnosis were 82.3, 13.0 and 4.1%, respectively. Cytological diagnosis was thus more accurate than clinical diagnosis. As the cause of erroneous diagnosis, association between cancer and benign tumor was seen frequently in 24 cases, followed by follicular carcinoma without nuclear atypia in 7 cases. Among 123 cases in which cells were not sampled, cystic degeneration of cancer lesion itself was found in 7 cases (6 of them had papillary carcinoma). Even when cystic fluid was aspirated, cystic formation of papillary carcinoma should always be considered. Intranuclear cytoplasmic inclusion appeared in papillary carcinoma (117/140), follicular carcinoma (8/20), anaplastic carcinoma (1/8) and medullary carcinoma (1/3), but none in benign tumor. Among other cytological findings, multinucleated cell, nuclear atypia, coarse granular chromatin, papillary cell arrangement and hypercellularity frequently appeared in malignant tumor. The complications related to fine needle aspiration were not seen except for subcutaneous hemorrhage. Fine needle aspiration cytology made it possible to predict the histological type and proved to be useful in planning for the preoperative therapy.