Next generation sequence (NGS) molecular multiple variant analysis, evaluation of histopatological and immunhistochemical findings in papillary thyroid cancer

PTC is the most common type of malignant thyroid tumor, accounting for more than 90% of thyroid malignancies. The incidence of thyroid carcinoma has increased rapidly over the last few decades, and it is making PTC the most common malignant endocrine tumor. Understanding the molecular pathogenesis of thyroid cancer in recent years holds great promise for the development of more effective treatment strategies. Although most PTCs spread slowly, some are associated with an aggressive clinical course. Extensive research has been carried out to identify different subtypes of PTC by histopathological and molecular parameters. Numerous molecular markers such as BRAF and RAS, have been proposed to aid in risk stratification. The concept of dividing PTC into high-risk and low-risk groups has recently gained attention because of its potential to predict prognosis and optimize the surgical and post-surgical management of patients with PTC. In this study, we aimed to determine the profile of somatic mutations detected in our department with the next generation sequencing (NGS) system in cases diagnosed with PTC and to compare molecular markers with histopathological and immunohistochemical parameters. The cases analyzed by NGS system among the thyroidectomy materials of the cases with a diagnosis of PTC, who were examined in the Department of Medical Pathology of Aydın Adnan Menderes University between 2019 and 2021, were included in the study. High molecular weight keratin (HMWK), Cytokeratin-19(CK19) and Galectin-3 stains were applied to all 74 cases immunohistochemically. In the study, histopathological findings that play a role in the prognosis of tumors, immunohistochemical CK19, galectin-3, HMWK expressions and pathogenic mutations detected in genes with NGS were evaluated. As a result of statistical analyzes, a significant relationship was observed between BRAF mutation and immunohistochemical galectin-3 and CK19 expression values. A significant correlation was observed between immunohistochemical galectin-3 expression, lymph node metastasis and lymphovascular invasion. A significant correlation was found between immunohistochemical CK19 expression and lymphovascular invasion. Immunohistochemical CK19, HMWK and galectin-3 expressions were significantly correlated among themselves. There was a significant relationship between tumor size and lymph node metastasis, lymphovascular invasion and capsule invasion. It was also observed that there was a significant relationship between lymph node metastasis and psammoma bodies and capsule invasion that histopathologically detected. In previous studies, the importance of BRAF positivity in terms of both poor prognosis and specific treatments has been shown recently. Therefore, analysis of mutations in these genes with NGS method in thyroid materials can be a guide in the follow-up and treatment of the cases. Although NGS results are more effective, an immunohistochemical alternative may be needed in the laboratory where NGS devices or immunohistochemical BRAF are not available. Our present findings have shown that the proportional increase in the percentages of Cytokeratin-19 and Galectin-3 staining, which is frequently has been using in many centers, is associated with molecular BRAF positivity. Due to cytokeratin-19 and Galectin-3 are also used for diagnostic purposes in many centers, their strong positivity may offer the potential to quickly guide the investigation of cases for molecular BRAF investigation without an additional immunohistochemical stain, tissue loss or method. The fact that BRAF mutation positivity is associated with a poor prognosis and this mutation is correlated with the immunohistochemical Cytokeratin-19 and Galectin-3 expression ratios; This suggests that the increase in the staining rates of these two immunohistochemical stains is associated with poor prognosis.