Characteristics of lymphocyte-infiltrating papillary thyroid cancer

Background: The tumor-promoting or tumor-suppressing role of tumor-associated lymphocytes remains a subject of debate. We examined thyroid cancer data from The Cancer Genome Atlas in an attempt to define the relationship between lymphocyte infiltrates and clinical and molecular presentations. Methods: Patient characteristics and transcriptome profiling were compared between groups dichotomized by the percentage of tumor-infiltrating lymphocytes of the primary tumor. Differentially expressed genes were subjected to functional enrichment analyses. Results: In 52% of the tumors, there was no lymphocyte infiltration. Papillary thyroid cancer with infiltrating lymphocytes was associated with classical histologic features, multifocality, and lymph node metastasis. Patients with lymphocyte-infiltrating cancer had a longer overall survival duration (log-rank P = 0.018). A total of 3151 differentially expressed genes were identified. Pathways related to immune response were upregulated, where the expression of several thyroid-related genes was downregulated. Conclusion: Papillary thyroid cancer with tumor-infiltrating lymphocytes is associated with an upregulation of immune response and cytokine production, along with a trend which suggests an overall survival benefit.