CCL17 and primary cutaneous T-cell non-Hodgkin lymphoma: It has been hypothesized that CCL17 expression by Langerhans cells, endothelial cells, and fibroblasts facilitates the recruitment of malignant T cells and Th2-polarized cells to the skin, contributing to the Th2-skewed tumor microenvironment typical of advanced CTCL (9, 10, 12, 21, 24).