ALK and anaplastic large cell lymphoma: i. Anaplastic large cell lymphoma (ALCL): differential diagnosis can be difficult in case of a rare sarcomatoid type of ALCL can exhibit spindle cell morphology with an overlapping immunophenotype, exhibiting positive staining for CD30, ALK, and smooth muscle actin, negative for epithelial membrane antigen and weak desmin expression; RANBP2-ALK fusion protein has not been reported in ALCL to date.