Small cell pattern of ALK‐negative anaplastic large cell lymphoma with double‐hit rearrangements of DUSP22 and TP63

In ALK‐negative anaplastic large cell lymphoma (ALCL), gene rearrangements of DUSP22 and TP63 are considered mutually exclusive. The former predicts a favorable prognosis, while the latter is generally unfavorable. We report the first case of ALK‐negative ALCL in a leukemic phase with small cell pattern transformation, harboring double‐hit rearrangements of the DUSP22 gene by inv(6)(p25q21) and TP63 gene by TBL1XR1‐TP63 inversion. Despite the resistance to chemotherapies, the patient remained in remission with allogeneic stem cell transplantation over 20 months. Recognizing this pathologically and genetically rare condition is needed for prompt diagnosis and therapeutic decision‐making in ALK‐negative ALCL.