Cross-sectional Study to Determine the Diagnostic Accuracy of Cytokeratin-19 Immunomarker in the Diagnosis of Thyroid Malignancy with Histopathology as Gold Standard

Background:Thyroid cancer, particularly papillary thyroid carcinoma (PTC), is the most common endocrine malignancy, with a growing incidence worldwide. Accurate differentiation between benign and malignant thyroid nodules is crucial for appropriate treatment and management. Histopathological analysis is the gold standard for definitive diagnosis, but immunohistochemistry (IHC) markers such as cytokeratin-19 (CK-19) have shown potential as valuable diagnostic aids in some cases with equivocal morphological appearances and have diagnostic dilemmas. CK-19 is known to be expressed in higher levels in malignant thyroid lesions, especially PTC. Aims:To study the diagnostic accuracy of CK-19 immunomarker in the diagnosis of thyroid malignancy with histopathology as the gold standard. Materials and Methods:The present study was carried out in Pathology Department, Bharati Vidyapeeth Deemed University Medical College and Bharati Hospital and Research Centre, Pune. It is a cross sectional, analytical, prospective and retrospective study. A total of 42 cases of thyroid nodules were included. IHC staining for CK-19 was performed on the paraffin-embedded tissue sections of these nodules. CK-19 expression levels were evaluated and compared between malignant and benign lesions. Receiver operating characteristic (ROC) curve analysis was used to determine the sensitivity, specificity and overall diagnostic accuracy of CK-19. Results:The study revealed that CK-19 expression was significantly stronger in malignant thyroid nodules, particularly in PTC, compared to benign nodules. Among the 42 cases included in the analysis, the sensitivity and specificity of CK-19 for detecting malignancy were both 92.9%. The ROC curve analysis showed an area under the curve of 0.971, indicating excellent diagnostic accuracy (P < 0.0001) with a 95% confidence interval of 0.922-1.000. Conclusions:CK-19 is a highly sensitive and specific immunomarker for distinguishing malignant thyroid nodules from benign ones, particularly in cases of PTC. The findings support the use of CK-19 as an adjunctive diagnostic tool in routine clinical practice to enhance the accuracy of thyroid cancer diagnosis and improve patient outcomes.