THYROID INCIDENTALOMA: RISK OF MALIGNANCY AS ASSESSED BY SONOGRAPHIC AND COLOR DUPLEX FEATURES
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Purpose: Our purpose was to determine the risk of malignancy of the incidentally discovered thyroid nodule by assessment of the sonographic and color duplex features. Patients and Methods: One hundred fifty eight non-palpable thyroid nodules in one hundred and seventeen patients underwent ultrasonographic and color duplex examinations and ultrasound guided fine needle aspiration biopsy with adequate cytological material. Each nodule was evaluated by nine specific sonographic and color duplex features: echogenicity, echostructure, size, shape, borders, microcalcifications, halo sign, vascularity and resistive index of the flow. All patients with malignant or suspicious lesions underwent surgery which was also done for non-cytological indications. Results: Thyroid malignancies were observed in 11 of the 158 nodules. The prevalence of malignancy in our study was estimated to be 7%. Intergroup comparison of the sonographic and color duplex features among the benign and malignant nodules resulted in indication of RI of more than 0.75 and presence of microcalcifications are both sensitive and specific predictor of malignancy (81.8% and 63.6% sensitivity & 98.6% and 87.1% specificity). Solid echotexture is sensitive (81.8%) but not a specific (28.8%) predictor. Marked nodal hypoechogenic ity, tall nodal shape and halo sign showed high specificity to predict malignancy (95.9%, 91.8%, and 82.3% respectively), nevertheless, all showed low sensitivity of 45.4%, 36.4% and 27.3%. Nodal hypoechogenicity, nodule size? 10 mm and nodules with blurred margins were non-reliable sonographic features for prediction of malignancy. Conclusion: Our study indicated that the presence of RI more than 0.75 is the only both most sensitive (81.8%) and most specific (98.6%) feature predicting malignancy of the thyroid nodules.