ALCLs with DUSP22 rearrangements express major histocompatibility complex class II. (A) DUSP22-rearranged ALCLs show increased expression of class II but not class I HLA genes. *P < .05; **P < .01; ***P < .001; ****P < .0001; n.s., not significant (Wilcoxon test). (B) Immunohistochemistry for HLA-DR in ALCLs with and without DUSP22 rearrangements. Original magnification, ×400. (C) DUSP22-rearranged ALCLs show significantly more tumoral staining for HLA-DR than either ALK-positive ALCL or other ALK-negative ALCLs (Wilcoxon test). (D) Model of immunogenic cues from DUSP22-rearranged ALCL cells and expected interactions with host reactive T cells. Red indicates upregulated molecules; green indicates downregulated molecules.