Rapid and (near) complete reduction in HRSCs during anti-PD1 treatment. (A-D) Patient with absence of HRSCs in rebiopsy (A-B, H&E stain; C-D, CD30 stain). (D) At rebiopsy after the start of anti-PD1 therapy, high-magnification images show scattered CD30⁺ cells resembling small activated immune cells in the tissue but no large HRSCs. (E-H) Patient with maintenance of HRSCs in rebiopsy (E-F, H&E stain; G-H, CD30 stain). Scale bars, 250 µm for H&E staining; 50 µm for CD30 staining. (I-L) WSI and gene expression of CD30 in paired samples. Patients with absence of HRSCs in rebiopsy (I-J) and patients with HRSCs detectable in rebiopsy (K-L). (J,L) Gene expression of TNFRSF8 (CD30) in normalized counts using NanoString technology (P = .0049 for entire cohort, Student t test). (I,K) CD30 immunohistochemically stained area as a percentage of WSI by digital image analysis (P = .0156 for entire cohort, 2-tailed paired Student t test). Red line, mean value.