Thyroid nodules are present in between 21-68% of the general population. The evaluation of these nodules to exclude thyroid carcinoma includes fine-needle aspiration cytology (FNAC) and a non-diagnostic cytology result occurs between 8-20% of the time. This retrospective cohort study aimed to determine the risk of malignancy in non-diagnostic thyroid nodule FNAC and to identify factors associated with malignancy. This is particularly important in managing patients with repeated non-diagnostic FNACs.
Over a six-year period, 495 patients with non-diagnostic thyroid nodule FNACs were followed up and 3% of these went on to develop thyroid cancer. This is lower than the estimated risk of a thyroid nodule being malignant (4-6.5%).
The study found the presence of calcifications to be the strongest predictor for malignancy. A smaller nodule size was also significantly associated with a higher risk of malignancy. Interestingly, no patients with repeatedly non-diagnostic FNACs were diagnosed with thyroid malignancy on follow up during the study.