Neoplastic T-cells in SS frequently express PD-1, and although gene mutations in CTCL commonly promote TCR-dependent proliferation, most CTCL cases show the “T-cell exhaustion” phenotype (PD1, TGT1 and CXCL13-positive) and could not proliferate after TCR stimulation. This evidence concerns the gene CXCL13 and primary cutaneous T-cell non-Hodgkin lymphoma.