Evaluation of Diagnostic Utility of the Immunohistochemical Markers in the Accurate Diagnosis of Thyroid Neoplasms: A Retrospective Study in a Tertiary Care Hospital of Pakistan.

Background Thyroid cancer is the most common endocrine malignancy across the globe and is among the fastest-growing cancers worldwide. Thyroid tumors are divided into differentiated and non-differentiated, with each having further subtypes, with papillary carcinoma being the most common one. Immunohistochemical (IHC) markers' studies play a crucial role in the accurate diagnosis of thyroid neoplasms. To the best of our knowledge, this topic has been the least researched in Pakistan. Objectives This study was designed to determine the diagnostic utility of immunohistochemical markers in the diagnosis of thyroid cancers in correlation with histopathology as the gold standard. Methods This retrospective, single-center study was carried out on 124 patients with thyroid cancer treated at our institution. The type of cancer, patient gender, and immunohistochemical markers used in each patient were recorded, and the sensitivity and specificity of the markers used in each tumor case were calculated. Results The mean age of patients was found to be 48.5 ± 15.6 years; 56 (45.2%) of the patients were male and 68 (54.8%) were female. Out of the 124 patients, 75 (60.5%) had papillary, 19 (15.3%) had medullary, 16 (12.9%) had anaplastic, and eight (6.5%) had follicular carcinoma, while six (4.8%) had primary thyroid lymphoma. Thyroglobulin was found to be a reliable tumor marker in both papillary and follicular tumors. The cluster of differentiation56 (CD56) negativity was a useful double panel study along with thyroglobulin in the confirmation of papillary carcinomas. Tumor markers used in medullary carcinoma include calcitonin, chromogranin, and synaptophysin. Cytokeratin AE 1 and vimentin were found to be useful for anaplastic tumors, while Ki 67 was a reliable marker for primary thyroid lymphoma.