Role of Lymphocytic Thyroiditis in Metastasis of Papillary Thyroid Carcinoma

Abstract

Objective: The role of chronic lymphocytic thyroiditis (CLT) in papillary thyroid carcinoma (PTC) is unclear. Studies have failed to demonstrate correlation of CLT with lymph node metastases (LNM) in part due to lack of standardized central lymph node dissection (CND). We investigate the incidence of LNM in specimens with CLT. Method: All OHSU patients who underwent total thyroidectomy with comprehensive ipsilateral CND for PTC between 2005 and 2010 were included. All specimens underwent genomic mutation analysis using a panel of known mutations. Reports were reviewed for tumor type, presence of lymphocytic thyroiditis, extracapsular extension, angiolymphatic invasion, and nodal metastasis. Results: A total of 139 patients met the selection criteria for this study. The overall rate of chronic lymphocytic infiltrate was 43.8%. The overall rate of central node positivity was 63%. There was a significantly higher proportion of central node positivity in the non-CLT patients (74% vs 49%, P = .003). There was also a higher rate of angiolymphatic invasion in the non-CLT patients (31% vs 15% P < .05). There was no significant difference in mean age, tumor size, and extracapsular extension. Molecular genotyping did not reveal a significant difference in the types of mutations found in both groups. Conclusion: Our data indicates a lower incidence of LNM in those with CLT ( P = .003), suggesting a potential protective role in tumor spread. The equal distribution of mutations in tumors with and without CLT argues against mutation-specific inflammation. Further research is needed to characterize the role of autoimmunity in thyroid cancer.