Correlative Study of Ultrasound Scan, Fine-needle Aspiration Cytology and Histopathology of Thyroid Swellings

Abstract

Abstract Introduction: Thyroid swellings are common clinical entities with a reported prevalence of about 10% of the adult population. As ultrasound technology is advancing, so is the detection of thyroid lesions, even if they are as small as a few millimetres in size. While fine-needle aspiration cytology (FNAC) is the standard procedure for thyroid nodule diagnosis; it involves risks and unnecessary costs. However, histopathological examination (HPE) is the gold standard for the classification of thyroid swellings. While individual characteristics of USS which increase the suspiciousness of malignancy, have been studied repeatedly but are inconclusive, we therefore need a comprehensive system of stratifying thyroid nodules and characterising them with confidence so that we can reduce the number of needless painful aspiration and biopsy procedures. Aim: This study aims to determine the diagnostic accuracy of ultrasound scans and FNAC in thyroid swellings by comparing them with HPE results. Materials and Methods: It was a prospective observational study conducted in a tertiary care centre over a period of 2 years. During this period, a total of 200 patients presented with palpable thyroid nodules in the surgery outpatient department out of which 160 patients were included in our study. All the patients underwent a triple assessment (clinical examination, sonogram and FNAC) and were later posted for surgery, the specimen obtained was sent for HPE. Data were collected and the results were analysed and compared. Results: One hundred and sixty cases with thyroid swellings were studied. Out of the 160 cases, 136 were female and 24 were male with female-to-male ratio of 5.6:1. Based on various ultrasound characteristics of thyroid nodules, each thyroid nodule was classified into ACR-TIRADS categories and then FNAC was done. On HPE diagnosis of 160 cases, 98 (61.3%) patients were benign and 62 (38.8%) patients were malignant. The results of histopathology were correlated with ultrasound features and statistical analysis was done calculating sensitivity, specificity, positive predictive value and negative predictive value for each feature. The sensitivity and specificity for irregular margin were 38.7% and 93.9%, for taller-than-wide were 21% and 100%, for punctate echogenic foci/microcalcification were 8.1% and 100%, for hypoechogenicity were 91.9% and 64.3% and for solid consistency were 69.4% and 76.5%. The risk of malignancy for TIRADS categories 2, 3, 4 and 5 in our study was 2.5%, 21%, 64% and 94%, respectively. In comparison with FNAC diagnosis and HPE, FNAC is 98.0% sensitive and 54.8% specificity in detecting benign lesions while 4.84% sensitivity and 97.96% specificity in detecting malignant lesions. Conclusion: ACR-TIRADS is a good predictor of malignancy. Individual characteristics such as solid composition, hypoechogenicity, irregular borders, taller-than-wide shape and microcalcifications were highly predictive of malignancy. FNAC is of greater help in the pre-operative diagnosis and should be treated as a first-line diagnostic test for thyroid swellings to guide the management though it is not a substitute for HPE.