Yuan Yu, Xuemei Qin, Shuxin Yan, Wenxia Wang, Yanlin Sun, Maohong Zhang

Myeloid sarcoma (MS) is defined as a tumor mass consisting of myeloid blast with or without maturation occurring at an anatomical site other than bone marrow with normal architectural effacement. It can also precede the onset of leukemia which is called non-leukemic MS. Non-leukemic MS is a kind of rare disease and easy to be misdiagnosed as other common malignancies due to the rarity and nonspecific manifestation. We herein report an unusual case of non-leukemic MS involving the vulva, vagina, and cervix in a female patient. The bone marrow aspiration and biopsy of the patient revealed no hematological abnormality. Immunohistochemical staining of the biopsies was strongly positive for myeloperoxidase, CD68, leukocyte common antigen (LCA), CD117, CD34, CD38, CD79a, and negative for cytokeratin (CK), epithelial memberane antigen (EMA), CD2, CD3, CD20, CD5, CD138. Then a diagnosis of non-leukemic MS was made. Unfortunately, our patient received only one cycle of chemotherapy consisting of cytosine arabinoside and daunorubicin, then refused any further treatment and died 4 months after diagnosis. Although systemic chemotherapy is widely accepted to be a promising strategy, its benefit still needs to be further assessed. Certain questions still need to be answered for this disease: 1) Why can approximately 20% of the patients with non-leukemic MS remain disease-free after local therapy alone? 2) How many cycles of chemotherapy are needed for these patients after achievement of complete remission? 3) What are the prognostic or risk factors in these patients who have no abnormality of karyotype, fusion genes, or gene mutation to predict responsiveness to chemotherapy and outcome? 4) What is the risk factor for relapse? The rarity of non-leukemic MS makes it almost impossible to conduct large-scale randomized trials, but judicious study for each patient with MS is helpful for a further understanding of the nature of the disease.