Ultrasound features of thyroid nodules predictive of thyroid malignancy as determined by fine needle aspiration biopsy

ABSTRACT

INTRODUCTION: Current guidelines recommend that in patients presenting with clinically palpable nodules or with an ultrasound finding of a thyroid nodule, one has to evaluate its risk for malignancy by proceeding with a fine needle aspiration biopsy (FNAB). The decision to do FNAB would depend on ultrasonographic features of the nodule, which include its size, hypoechogenicity, presence of microcalcifications, increased central vascularity, infiltrative margins, and taller than wide measures on transverse plane. Elastography, a measure of tissue stiffness, is now also being utilized as another feature that has a positive correlation with malignancy. This study hopes to determine which among the abovementioned ultrasonographic features would best correlate with a higher risk for thyroid malignancy among adult patients who had undergone ultrasound guided FNAB.METHODOLOGY: A prospective study was done in a cohort of all Filipino patients 19 years old and above who underwent ultrasound guided FNAB of the thyroid nodule/s from July to December 2013 at the Radiology Section of The Medical City, Pasig City, Philippines. Specimen obtained from FNAB were then reviewed by a pathologist to determine its cytopathology and categorized based on the Bethesda System of Classification. The cytopathology reports were correlated with the features seen on the patient's thyroid ultrasound to determine which characteristic would be predictive of malignancy.RESULTS: A total of 100 patients underwent ultrasoundguided FNAB, from which 157 nodules were biopsied. 27 nodules were excluded from the analysis due to non-diagnostic or unsatisfactory (Bethesda Category I) findings on cytopathology. Among the 100 patients, 86% of which were females with the mean age of 41 ± 11.31 in those found to have malignant cytopathologic diagnosis. Of the 130 nodules biopsied, 115 nodules were identified as benign (Bethesda Category II) while 15 were identified to be malignant or suspicious for malignancy (Bethesda Category III-VI). Each of the five sonographic features that were predictive of malignancy was compared between the two outcome groups (benignversus malignant). Among them, only the presence of microcalcifications on ultrasound showed to be significantly correlated with malignancy with an odds ratio of 11.3. Ultrasound evaluation with elastography was only performed on 24 nodules and hence results were inconclusive. A nodule possessing more than two of the ultrasound features that were predictive of malignancy was more likely to be malignant on cytopathology (p value of 0.00).CONCLUSION: The presence of microcalcifications on thyroid nodules as seen on ultrasound is a significant predictor of malignancy and remains to be consistent locally as with foreign studies. Nodules that were proven to be malignant on cytopathology presented with more of the ultrasound features that are said to be predictive of malignancy.