ALK and anaplastic large cell lymphoma: We have successfully established and characterised PDX models from biopsies of multi‐agent chemotherapy‐refractory (Patient 2, MTK‐A‐x), and both multi‐agent chemotherapy‐refractory‐ and crizotinib‐resistant (Patient 1, MGS‐A‐x; Patient 3, GR‐ALCL‐1) paediatric CNS‐positive, r/r ALK+ ALCL patients.