Despite many clinical trials of CD19‐targeted CAR T cells for the treatment of B‐cell acute lymphoblastic leukemia (B‐ALL) having been reported, few studies of CD19 CAR T therapy for isolated refractory/relapsed (r/r) extramedullary ALL (EM‐ALL) patients have been published. The gene discussed is CD19; the disease is B-cell acute lymphoblastic leukemia.