Infiltration of mixture of immune cells is associated with good prognosis in patients with differentiated thyroid cancer.

Abstract Immune responses against differentiated thyroid carcinomas (DTC) have long been recognized but its effect on patients prognosis is a matter of debate. In order to investigate the role of immune cell infiltration in the progression of DTC, we studied 398 patients - 253 with papillary and 13 with follicular thyroid cancers, as well as 132 with nonmalignant tissues. Immune cell infiltration was identified using CD3, CD4, CD8, CD20, CD68, and FoxP3 immunohistochemical markers. We colocalized CD4/IL-17 in order to identify Th17 lymphocytic infiltration. We also colocalized CD33/CD11b in order to identify myeloid derived suppressor cells (MDSCs) infiltration. Immune cells infiltrated malignant tissues more often than benign lesions. We observed a close correlation among CLT, tumor infiltrating lymphocytes, tumor-associated macrophages and cell molecular profile, suggesting this profile may be related to antitumor immune response. The presence of chronic lymphocytic thyroiditis (CLT), CD68+, CD4+, CD8+, CD20+, FoxP3+, Th17 and MDSCs was associated with clinical and pathological features of lower tumor aggressiveness and a more favorable patient outcome. A log-rank test confirmed an association between CLT, tumor-associated macrophage infiltration, and CD8+ lymphocytes and an increased disease-free survival. In conclusion, immune cell infiltration and the presence of concurrent CLT helped characterize specific tumor histotypes and were associated with favorable prognostic features.