Diagnostic accuracy of fine needle aspiration cytology in nodular goitres with clinico-pathologic correlation

Abstract

Background: FNAC is now one of the initial diagnostic modalities for thyroid nodules and can be used in association with clinical diagnosis especially to rule out malignancy thereby avoiding unnecessary surgeries for benign pathologies. We evaluated the usefulness and diagnostic accuracy of fine needle aspiration cytology as an initial investigation in patients with nodular goitres by comparing it with histopathology.

Methods: A combined retrospective and prospective study comprising 61 patients admitted and operated for nodular goitres over a period of two years at a tertiary hospital was carried out. All patients were evaluated by detailed history, clinical examination, serum thyroid hormonal levels and FNAC which were divided into four categories namely benign, malignant, indeterminate and nondiagnostic. All the patients were subjected to surgery and the thyroid specimens were sent for histopathological evaluation. Finally clinical, cytological and histopathological correlation was analyzed and usefulness of FNAC in detecting malignancy was evaluated.

Results: In present study 47.54% cytologies were benign, 34.42 were indeterminate, 11.47% were malignant and 6.55% were nondiagnostic. For neoplastic lesions, FNAC had sensitivity of 84.37%, specificity of 96%, PPV of 96.42%, NPV of 82.75% and diagnostic accuracy of 89.47%. For carcinoma, FNAC had a sensitivity of 70%, specificity of 100%, PPV of 100%, NPV of 94%, false negative rate of 6%, false positive rate of 0% and diagnostic accuracy of 94.73%.

Conclusions: FNAC with its very high specificity, negative predictive value and diagnostic accuracy, approaching 100% can help to rule out malignancy in most cases of thyroid swellings and prevent unnecessary surgeries.