Rate of Malignancy in Exophytic Thyroid Nodules

Background There are ultrasonography (US) features suggested to be associated with a higher risk of malignancy in thyroid nodules. However, exophytic appearence of thyroid nodules has not been studied previously. Objectives To evaluate US features, and cytological and histopathological findings in exophytic thyroid nodules. Patients and Methods Patients with an exophytic thyroid nodule who underwent fine needle aspiration biopsy (FNAB) between January and July 2015 were evaluated prospectively. Demographical data, US features, and cytology results were noted and histopathological findings were determined in operated patients. The results were compared with non-exophytic nodules of age and sex matched patients. Results Data of 253 exophytic nodules in 247 patients and 529 non-exophytic nodules in 357 patients were analyzed. Hypoechogenity, mixed texture, and absence of peripheral halo were significantly higher in exophytic nodules (P < 0.001, P < 0.001, and P = 0.018, respectively). Nondiagnostic, atypia of undetermined significance/follicular lesion of undetermined significance and suspicious for malignancy cytology results were significantly higher in exophytic nodules (P = 0.002, P < 0.001 and P < 0.001 respectively). 6.7% of exophytic nodules and 1.9% of non-exophytic nodules had malignant cytology (P = 0.001). Histopathologically, 35 (47.9%) of 73 exophytic nodules and 18 (24.3%) of 74 non-exophytic nodules were malignant (P < 0.01). Capsular invasion was higher in the malignant exophytic group (53.5% vs 14.3%, P = 0.027). US features other than hypoechoic pattern which was higher in the malignant group were similar in benign and malignant exophytic nodules. Conclusions Exophytic nodules seem to carry a higher rate of malignancy both cytologically and histopathologically. Suspicous US features except hypoechoic pattern were not higher in malignant compared to benign exophytic nodules.