Cytological and Ultrasound Findings in Indeterminate Lesions of the Thyroid Gland

Objectives Thyroid nodules are common, and the majority are discovered incidentally on physical examination or imaging studies. Certain features on ultrasound (US) have been traditionally associated with malignant lesions and others with benign lesions. The aim of this study was to investigate the efficacy of US in determining malignancy in thyroid lesions diagnosed as indeterminate or malignant according to the cytological findings on fine needle aspiration biopsy (FNAB). Methods The records of 270 patients, referred to a single clinic with multinodular goiter were evaluated retrospectively, and 400 thyroid nodules sized larger than 5 mm in diameter were selected for the study. After exclusion of nodules classified as benign according to the FNAB findings, 203 thyroid nodules were included in this study. The nodules were divided into two groups on the basis of the FNAB findings: group 1 consisted of 82 nodules with indeterminate cytology and group 2 consisted of 121 nodules with cytological findings of malignancy or suspicious for malignancy. Results The diagnostic accuracy of ill-defined borders was 69.5% in group 1 (indeterminate) and 56% in group 2 (p=0.04). The diagnostic accuracy of solid composition was 50% in group 1 and 73% in group 2 (p=0.01). Positive correlation was demonstrated between ill-defined margins and malignant histology in group 1 (r=0.411, p=0.001), and between microcalcifications and malignant histology in group 2 (r=0.247, p=0.002). Conclusions In this study, the only US finding shown to be correlated with malignant histology in thyroid nodules of indeterminate cytology on FNAB was ill-defined margins. More precise US criteria are needed to decide on surgery in patients with thyroid nodules of indeterminate cytology.