Introduction: Some studies have shown largest thyroid nodule size, especially â‰¥4cm that can predict malignancy and reduce fine needle aspiration biopsy (FNAB) accuracy. Therefore, this study is designed to evaluate relationship between thyroid nodule sizes with malignancy and its effect on FNBA accuracy. Materials and Methods: a retrospective analytical study design aims to investigate all patients with thyroid nodules who referred to surgery department of Imam-Khomeini Hospital of Mazandaran University of Medical Sciences in Sari from 20 March 2008 to 22 March 2014. We collected patientâ€™s demographic data, nodules size, FNAB reports and final pathology (after surgery) reports from their medical records. All data were analyses performed by SPSS18. Results: 167 patients (153 women) with mean age of 41.56±13.24 years old were enrolled for this study. In final pathology; 38 patients (22.8%) had malignant nodules. The mean age of patients with or without malignant nodules were 34.93±11.86 and 42.37±12.26 years old, respectively (P=0.002). The mean size of benign and malignant nodules were 2.91±1.29 cm and 3.38±1.86 cm, respectively (P=0.15). 25.2% of
Thyroid cancer, thyroid nodules, Fine needle aspiration biopsy.