Leukemia was originally named for the abnormally high number of white blood cells in the peripheral blood of patients. It is now clear that patients with “leukemia” do not necessarily have elevated peripheral blood leukocytes at the time of initial diagnosis, and with further breakdown of leukocyte subgroups, approximately 20% to 30% of patients have undetectable leukocytes in their peripheral blood. Depending on the course of the disease at the time of presentation, patients may present with varying degrees of decreased hemoglobin and platelets, fever from infection, and enlarged liver, spleen, lymph nodes, and skeletal pain.
Patients with peripheral leukocytosis may be distinguished from “leukemia-like” reactions of the blood caused by severe infections and other solid tumors, but neither of the latter two is seen in the peripheral blood or bone marrow.
Patients with normal or reduced peripheral blood leukocytes should be differentiated from immune system disorders, hypersplenism after cirrhosis, and specific infections (such as viruses or tuberculosis), usually with a history and specific symptoms. There are also other benign and malignant diseases of the hematologic system, such as aplastic anemia, myelodysplastic syndromes (MDS), lymphoma or myeloma, etc., which need to be identified by bone marrow aspiration.