[Acute promyelocytic leukemia recurrence diagnosed due to granulocytic sarcoma of the external auditory canal].

A 47-year-old man was diagnosed with acute promyelocytic leukemia (APL) accompanied by pancytopenia and left forearm swelling. Complete remission was achieved with remission induction therapy using all-trans retinoic acid (ATRA), and consolidation therapy was completed. Three months after the treatment, left ear closure was observed, and a mass lesion was found in the left external auditory canal. An initial tumor biopsy only revealed inflammatory cell infiltration. Moreover, the tumor's rebiopsy performed 3 months later revealed MPO-positive and CD68-positive granulocyte infiltration. Furthermore, the rebiopsy revealed 4.9×10 copies/µgRNA of PML/RARα, the patient was diagnosed with locally recurrent APL. A bone marrow examination 2 weeks later confirmed an increase in myeloblasts and promyelocytes for the first time since the confirmation of remission. Therefore, it was diagnosed as bone marrow recurrence. Reinduction therapy using ATRA and arsenic trioxide again led to complete remission, after which autologous peripheral blood stem cell transplantation was performed. Currently, complete remission is being maintained. In this case, the recurrence of the external auditory canal lesion preceded the bone marrow recurrence. Therefore, it is important to note the nonspecific leukemia recurrence patterns of the external auditory canal.