Expression and incidence of ERBB4-truncated transcripts. (A) Incidence of I20ΔERBB4 expression analyzed by qRT-PCR in a total (tot) of 170 cryopreserved and formalin-fixed and paraffin-embedded T-NHL samples (51 PCTL-NOS, 44 ALK-positive ALCL, and 75 ALK-negative ALCL). (B) Quantification of I20ΔERBB4 and TNFRSF8 transcripts by ddPCR assay in selected ALCL cases. (C) Western blot analysis of the HEK293T cell line transfected with wild-type (wt) ERBB4 and 2 ALCL samples (1 ERBB4-positive and 1 ERBB4-negative). Tissue lysates from an ERBB4-positive sample indicated the expression of a 50-kDa truncated ERBB4 protein, which was highly phosphorylated and correlated to MMP9 expression. (D) Representative hematoxylin and eosin (H&E), TNFRSF8, ERBB4, and MMP9 immunohistochemical staining in an ERBB4-negative and an ERBB4-positive ALCL sample (original magnification ×20). (E) Box plot showing immunohistochemical quantification of MMP9 expression in ALK-negative ALCL patients (8 ERBB4-negative and 7 ERB-positive). Quantitative analysis indicates percentage of anaplastic cells with a score of 3+. Measurements were performed in 3 independent tissue areas (***P < .001). MMP9, matrix metalloproteinase 9; TNFRSF8, tumor necrosis factor receptor superfamily, member 8.