Hematoxylin and eosin (H&E) and immunohistochemical staining of ALCL. (A) ALK+: Hallmark cells demonstrated by H&E staining and tumor cells positive for ALK, CD30, and epithelial membrane antigen (EMA); (B) ALK−: Hallmark cells demonstrated by H&E staining and tumor cells positive for CD30 but negative for ALK and EMA staining.