Pembrolizumab treatment of mycosis fungoides with PD-L1 structural variants. (A) Depiction of discovered PD-L1 structural variants. (B) Immunohistochemical staining of PD-L1 using 22C3 (i) and E1L3N (ii) clones for 3 pembrolizumab-treated patients. (C) Photographs of 3 patients with MF and LCT treated with pembrolizumab-based therapy before (i) and after (ii) treatment. (D) A swimmer’s plot representation of the responses to pembrolizumab-based therapy.