ALCLs with DUSP22 rearrangements lack phosphorylated STAT3 protein. (A) Immunohistochemistry for pSTAT3^Y705 in ALK-positive ALCL and DUSP22-rearranged ALCL; note internal positive control staining in endothelial cells in the bottom image. Original magnification, ×400. (B) Results of pSTAT3^Y705 staining in 334 FFPE ALCLs independent from the frozen discovery set, stratified by genetic subtype. (C) Prognostic significance of DUSP22 rearrangement in 59 systemic ALK-negative ALCLs that are negative for pSTAT3^Y705 by immunohistochemistry (<20% of tumor cells with nuclear staining; log-rank test; see also supplemental Tables 6 and 7).