Objective. Thyroid cancer is the most common endocrine malignancy in humans. Ultrasound guided fine needle aspiration cytology (FNAC) is now considered the best diagnostic tool for the evaluation of any thyroid nodule. Thyroid cytology is graded from Thy1 to Thy5 with Thy3 being the most challenging in diagnosis. Our aim was to identify the risk of malignancy in Thy3 cytology in our centre. This risk should be explained to the patient before taking any decision.

Methods. One hundred and one patients were included in our study. All patients had Thy3 cytology on preoperative ultrasound scan guided FNAC. All patients had diagnostic hemithyroidectomy. The results from the histology were compared with the cytology findings and the rates of malignancy were identified.

Results. Of the 101 patients, 17 were males and 84 females. Average age for diagnosis was 52.4±15 years of age. Patients were classified into three groups; patient who had completely benign histology (n=70), patients who had incidental finding of micro-carcinoma after diagnostic hemithyroidectomy (n=10), and patients who had thyroid macro-carcinomas (n=21). Total rate of malignancy was 30.7% when combining both the malignant and the incidental groups and 20.8% when excluding the incidental group.

Conclusion. Our rates of malignancy in Thy3 cytology are similar to the literature. These rates should be explained clearly to the patient during the preoperative counselling. Future advances in biomarkers technology may help to improve the preoperative diagnostic accuracy and reduce the rate of unnecessary thyroid surgery.