A previously healthy 40-year-old male presented with a 2-week history of fever and abdominal discomfort that was resistant to empirical broad-spectrum antibiotic treatment. The patient’s blood cell count and complete biochemical panel was normal, except for an increased lactate dehydrogenase level. Ultrasonography and computed tomography of the abdomen showed a large, soft tissue mass had infiltrated superior part of the spleen. Splenectomy with total tumor mass removal were performed. The pathological examination of the tumor tissue confirmed diagnosis of isolated myeloid sarcoma with monoblastic differentiation. Despite intensive antileukemic therapy, patient died four months after diagnosis was established.