Extramedullary Relapse of Acute Promyelocytic Leukemia in the Middle Ear after All-Trans Retinoic Acid Combined with Chemotherapy.

A 69-year-old man with acute promyelocytic leukemia in molecular remission and no detectable PML::RARA transcripts in his peripheral blood cells developed acute otitis media. After 10 months, tympanomastoidectomy was performed for suspected secondary cholesteatoma. A histological examination confirmed extramedullary relapse with PML::RARA-positive cell infiltration. The patient achieved a second molecular remission after treatment with arsenic trioxide. Our findings suggest that (1) a diagnostic sample may be obtained from mastoid air cells rather than from the middle ear cavity, (2) molecular remission does not preclude extramedullary relapse, and (3) all-trans retinoic acid and arsenic trioxide combination therapy may reduce the risk of extramedullary relapse.