When the expression level of siglec-7 was examined in T cells from CTCL lesional skin and control skin specimens, it was found that a part of the benign CD4 T cells in CTCL lesions express siglec-7, while the expression of siglec-7 on the malignant T cells, benign CD8 T cells in CTCL, and control skin T cells was limited (Figures 3A, B). The gene discussed is CD4; the disease is primary cutaneous T-cell non-Hodgkin lymphoma.