Myeloid Sarcoma of the Paranasal Sinuses in a Patient with Acute Myeloid Leukemia

: Myeloid sarcoma (MS) is an uncommon extramedullary malignant tumor, and often represents a subgroup of acute myeloid leukemia (AML). MS of paranasal sinus origin is extremely rare. We report an uncommon case of sinonasal MS associated with AML, who was successfully treated with hematopoietic stem-cell transplantation. A 39-year-old male was admitted with complaints of left nasal obstruction and proptosis. Computed tomography and magnetic resonance imaging identified a left ethmoidal mass involving the maxillary sinus, the orbit, and the skull base. Nasal endoscopic examination detected a whitish homogeneous mass occupying the left nasal cavity. Although accumulation of atypical lymphocytes was suspected based on initial pathological inspection, immunohistochemical analysis showed myeloperoxidase-positive myeloid cells. Together with concomitant leukocytosis (149,000/µL) composed of myeloid blast cells and excess of myeloblasts in the bone marrow, the patient was diagnosed as sinonasal MS with AML with maturation (French-American-British Classification M2). The patient was treated by chemotherapy (remission induction therapy with daunorubicin and cytarabine; salvage chemotherapy with high-dose cytarabine), radiotherapy (30 Gy in 10 fractions) and allogeneic hematopoietic stem-cell transplantation, and followed up for 12 months with no recurrence. Early diagnosis is critical for the best improvement of MS. MS of the paranasal sinuses may easily be misdiagnosed as malignant lymphoma or poorly differentiated carcinoma. Prompt hematological and immunohistological investigations with suspicion of MS are essential for correct diagnosis. Furthermore, we concisely review nine previously reported patients with MS and indicate the importance of hematopoietic stem-cell transplantation for good prognosis.