Ultrasound-guided fine-needle aspiration biopsy and ultrasonographic features of infracentimetric nodules in patients with nodular goiter: correlation with pathological findings.

We evaluated the usefulness of ultrasound-guided fine-needle-aspiration biopsy (US-FNAB) for infracentimetric nodules. In addition, we used sonography to assess the risk of malignancy of thyroid nodules, and we evaluated the extent of disease in infracentimetric cancers. The cytopathological results of 472 US-FNABs from 207 nodular goiter patients (170 women, 37 men; mean age, 51.5 +/- 13.1 yr) seen between 1999 and 2004 were categorized into five groups: inadequate, benign, suspicious, follicular neoplasm, and malignant. There were 145 infracentimetric nodules and 327 supracentimetric nodules. All patients underwent surgery. Final histopathological results correlated with cytologic results. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of US-FNAB for infracentrimetric nodules were 96.3%, 71.2%, 44.8%, 98.8%, and 76.1%; and for supracentimetric nodules, these values were 98.1%, 63.1%, 35.6%, 99.4, and 69.1%, respectively. There were no significant differences between infracentimetric and supracentimetric nodules. More thyroid cancer could be detected in infracentimetric nodules that were hypoechoic or had fine calcification on ultrasonography (which may be helpful in discriminating which nodules are appropriate for FNAB) than in supracentimetric nodules. However, logistic regression analyses showed that no single variable was predictive of malignancy in infracentimetric nodules. The malignancy rate in infracentimetric nodules was 21.4%. In this subgroup, 4 of 31 patients (12.9%) had multifocal tumors at surgery, 3 of 31 had extrathyroidal invasion, and 1 had a metastasis to the lung. In addition, at surgery, 11 of 55 tumors (20%) larger than 1 cm were multifocal. In conclusion, small tumor size does not guarantee a low risk of thyroid cancer, and US-FNAB may be useful tool for diagnosing malignant infracentimetric nodules.