CD4 and thyroid cancer: Based on the available literature and our previous work, we hypothesized that the circulating leukocyte populations, specifically suppressor (Tregs, MDSCs, effector memory T cells) and effector cells (CD4+ T cells, CD8+ T cells, gamma-delta T cells, NK cells, central memory T cells), in patients with high-risk thyroid cancer would be different from those in low-risk thyroid cancer.