Myeloid Sarcoma in the Nasal Cavities that Developed during the Course of Acute Myelomonocytic Leukemia

In December 2006, a 95-year-old Japanese woman was transferred to our hospital for the evaluation of her leukocytosis. In September 2006, the patient was medicated for hypertension by her family physician and she was found to have leukocytopenia (2,500/mL) without abnormal cells in the peripheral blood (PB). During the middle of November, the patient’s white blood cell (WBC) count was found to be elevated. Upon admission to our hospital, the patient had no complaints and presented no remarkable findings on physical examination. She had no clinical evidence of dementia. A complete blood count showed WBC count of 58,300/mL (myeloblasts 7%, neutrophils 27%, metamyelocytes 1%, monocytes 58%, and lymphocytes 7%), hemoglobin of 9.1 g/dL, and platelet count of 149,000/mL. Most of the monocytes were immature and positive for CD11b, CD13, CD14, CD15, CD33, and CD64. Hypersegmented neutrophils and giant neutrophils were seen. Since the patient and her family refused bone marrow aspiration (BMA), we considered from the above PB profile and the progressive clinical features that the patient likely had acute myelomonocytic leukemia (AMMoL). Following chemotherapy with low-dose cytarabine (Ara-C) (20 mg/day subcutaneously, on days 1-25), her WBC count gradually decreased, and myeloblasts and abnormal monocytes disappeared. Her general condition was seen to be stable. At the end of March 2007, her WBC count again elevated with myeloblasts and abnormal monocytes (15% and 8%, respectively) being around 10,000/mL. BMA could be carried out at that time, and it showed elevation of myeloblast and monoblast percentages (19.3% and 22.5%, respectively) (Fig. 1). Blasts were positive for myeloperoxidase (MPO) and monoblasts were positive for non-specific esterase, CD11b, and CD64. Since dysplasia in the myeloid series, characterized by hypersegmented neutrophils, giant neutrophils and Pelger-Huet nuclear anomaly, was detected, a diagnosis of AMMoL, which had been most likely progressed from myelodysplastic syndrome (MDS), was further confirmed. The possibility that the present case was chronic myelomonocytic leukemia could be excluded because of the presence of excessive myeloblasts. Chromosomal analysis of BM revealed no abnormalities. At that time, the patient also presented bilateral nasal obstruction with swelling. A computed tomography (CT) scan revealed a soft tissue mass occupying both of the nasal cavities by involving the nasal septum (Fig. 2a, b). No destruction of the bone was evident. Biopsy of the tumor showed diffuse proliferation of large mononuclear cells which was covered by focally erosive mucosal tissue with the infiltration of mature neutrophils and plasma cells. The large mononuclear cells had immature-appearing nuclei with mitotic features and weakly eosinophilic cytoplasm. (Fig. 3a, b). Immunohistochemically, the cells were positive for MPO, a1antitrypsin (AAT), lysozyme, CD4, CD15, CD68, and CD163, and were negative for CD3e, CD20, CD34, CD56, and CD123 (Fig. 4). Among the proliferating cells, MPO, AAT, lysozyme, and CD68 were positive in the vast majority of cells, while the positive rates of CD15, CD4, and CD163 were estimated to be 80%, 60%, and 40%, respectively. Although these findings are not precise, the proliferating cells appeared to be composed of granulocytic, monocytic, and granulomonocytic (a cell having both granulocyte-related and monocyte-related molecules) lineages. Based on these findings, the lesion was diagnosed as one of myeloid sarcoma (MS), and could be classified as myelomonocytic sarcoma. Chemotherapy consisting of low-dose Ara-C (20 mg/day subcutaneously, on days 1-14) and aclarubicin (10 mg/day intravenously, on days 1-4) resulted in a decrease of WBC count