The management of non-diagnostic fine needle aspiration biopsy of thyroid nodules has been a dilemma. The purposes of this study were to analyze the characteristics and the results of follow up of non-diagnostic aspirates and to evaluate the management strategy.

A retrospective review was conducted on the patients who underwent fine-needle aspiration of thyroid nodules that were found on a health examination. The patients' records were assessed for the demographics, the ultrasound findings and the pathologic findings.

The initial non-diagnostic rate was 35%. The nodule size (≤10 mm) and cystic nodule were related to a high rate of non-diagnostic results. The common causes of non-diagnostic results by pathologic description were reducedcellularity (59.3%) and blood (28.2%). Among the 62 initially non-diagnosed patients, 2 patients were confirmed to have malignancy and 32 patients (51.6%) were lost from follow-up. Reaspiration was performed in 18 patients and 6 patients still resulted non-diagnostic aspirates.

Nodule size and cystic nodule were associated with a high rate of non-diagnostic results. Non-diagnostic results of thyroid nodules may be associated with a relatively high frequency of follow up loss, and non-diagnostic results may be associated with a probability of malignancy. So, non-diagnostic results should not be considered just benign, and clinicians should recommend a repeat exam for such patients.