Endocrine Abstracts

Objective: Fine needle aspiration biopsy (FNAB) is a reliable and safe method to distinguish benign and malignant thyroid nodules. FNAB has two major limitations: nondiagnostic and suspicious cytology results. There is uncertainty about clinical approach to the nondiagnostic FNAB in thyroid nodules. Our aim was to evaluate the ratio and reasons of nondiagnostic results, and the ratio of malignancy in these nodules.

Method: About 2082 patients and 3404 nodules in these patients who referred to the thyroid disease outpatient clinic between 2005 and 2008 were analyzed, retrospectively. Nodules with suspicious ultrasonographic images and two nondiagnostic cytology were given to surgery. Nodules reported as nondiagnostic in two cytologies, but without suspicious ultrasonographic images were taken to clinical and ultrasonographic follow-up.

Results: FNAB was performed in 3404 nodules. After the first ultrasonography guided FNAB, the rate of nondiagnostic cytology was 9.3% and a second FNAB was repeated in this group. Cytology was reported as nondiagnostic again in 10.8% of these. According to nodule size, 14.6% of infracentimetric nodules and 7.9% of supracentimetric nodules were nondiagnostic (P<0.001). The ratio of nondiagnostic results was 8.9% in solid nodules, 12.3% in mixed nodules and 13.8% in cystic nodules (P=0.08). 14 patients with nondiagnostic cytology underwent operation and histopathologically malignancy ratio was found to be 64.3% (n=9).

Conclusion: According to our results, the ratio of nondiagnostic cytology results was 9.3%. Nondiagnostic cytology was found to be related to the size of the nodule. In the literature malignancy ratio in nondiagnostic cytology is reported between 9 and 37% in different studies, but ours was 64.3%. The reason for higher malignancy rates in our study may be preference of surgical management not in all patients with nondiagnostic cytology but in patients with clinically and ultrasonographically suspicious nodules. Considering this result, nondiagnostic cytologies might not be of benign cytology and should be evaluated carefully.