Fine-needle aspiration cytology of the thyroid: ten years experience in a community teaching hospital

We present our experience of fine-needle aspiration (FNA) cytology of the thyroid in a community hospital setting and discuss the cancer probability of the indeterminate FNA results. There were 1,621 FNAs, 401 of which have follow-up thyroidectomies during a 10-yr period. The initial FNA diagnoses of these 401 cases were benign non-neoplastic (BNN) 159, malignant 34, atypical 33, suspicious 19, follicular neoplasm (FN) 88, follicular lesion (FL) 51, and inadequate 17. There were no false-positive cases. Cancer was found in 11 cases diagnosed as BNN (7%), 6 cases were due to sampling errors (incidental microcarcinomas), and 5 cases were due to failure to identify focal atypia in the smears of a follicular variant of papillary carcinoma. The false-negative rate was 3%, with the exclusion of cases of incidental microcarcinomas. Among the indeterminate FNA results, the follow-up operations revealed malignant tumors in 16 of 33 (48%) cases of atypical, 13 of 19 (68%) cases of suspicious, 29 of 88 (33%) cases of FN, and 7 of 51 (14%) cases of FL. Malignant tumors were also found in 2 of 17 (12%) of inadequate specimens with follow-up. When compared to the cancer rate (3%) for FNA diagnosis of BNN, the likelihood of finding cancer in the thyroidectomy is 5 times more for a FL, 11 times more for a FN, 16 times more for atypical, and 23 times more for suspicious. The sensitivity and specificity are 87 and 100%, respectively.