Study of Immunohistochemical Markers (CK-19, CD-56, Ki-67, p53) in Differentiating Benign and Malignant Solitary Thyroid Nodules with special Reference to Papillary Thyroid Carcinomas.

Introduction: Solitary Thyroid Nodule (STN) has provoked increased concern owing to higher incidence of malignancy. The inter and intra observer variation in the histomorphological diagnosis of Papillary Thyroid Carcinomas (PTC) may sometimes pose a diagnostic difficulty.

Aim: This study was undertaken to analyse immunohistochemical (IHC) markers (CK-19, CD-56, p53, Ki-67) to differentiate between benign and malignant surgically resected STN along with their utility in the identification of PTC.

Materials And Methods: The present cross sectional study was conducted over a period of 4 years. A technique of manual tissue array was employed for cases subjected to IHC. The primary antibodies used were CK-19, CD-56, p53 and Ki-67. Analysis of the expression of IHC markers (p53, Ki-67) to distinguish between benign and malignant STN was done. Evaluation and correlation of expression of IHC markers (CK-19, CD-56) to determine its utility in reaching definitive diagnosis and assessing prognosis of PTC was tried. Results were subjected to statistical analysis. The results were considered to be significant when the p-value <0.05.

Results: Out of the 160 cases of surgically resected STN specimens, 68 cases were non-neoplastic, 24 cases were benign and 68 cases were of malignant tumours (7 cases of follicular carcinoma (FCa), 61 cases of PTC). CK-19 was found to be a sensitive (83.61%) and a highly specific positive marker (100%) for the diagnosis of PTC. The difference in CD-56 expression between PTC and non-PTC group was found to be highly statistically significant. CD-56 was found to be a sensitive (85.86%) and specific (82.25%) negative marker in differentiating PTC from follicular lesions/neoplasms. The difference in p53 expression between the malignant and non-malignant STN cases was found to be highly statistically significant with a sensitivity and specificity 85.29% and 70.65% respectively. The statistical difference in mean Ki-67 Labeling Index (LI) was found to be significant between PTC versus FA, PTC versus non-neoplastic lesions, FA versus FCa and FVPTC versus FA.

Conclusion: The panel of four IHC markers (CK-19, CD-56, p53, Ki-67) may be used for differentiating doubtful benign STN cases from malignant ones and also for definitive diagnosis of PTC along with histopathological examination.