Diagnostic Approach to Leukocytosis with Splenomegaly

Primary Diagnostic Considerations

The combination of leukocytosis and splenomegaly should immediately raise suspicion for chronic myeloid leukemia (CML), which classically presents with myeloid hyperplasia, splenomegaly, neutrophil leukocytosis, thrombocytosis, and basophilia, according to the American Society of Hematology 1, 2, 3
CML is the prototypical presentation of leukocytosis with splenomegaly, characterized by the Philadelphia chromosome t(9;22) or BCR-ABL fusion gene in almost all patients, as recommended by the National Comprehensive Cancer Network 1, 2, 3
Approximately 50% of patients with CML are asymptomatic at diagnosis, and the median age at diagnosis is around 60 years, according to the American Cancer Society 1, 2, 3
Chronic neutrophilic leukemia (CNL) presents with leukocytosis and frequently splenomegaly, though it is rare, as noted by the European Hematology Association 4
Chronic eosinophilic leukemia (CEL) can present similarly with splenomegaly and leukocytosis, as reported by the American Society of Hematology 4

Assess for left shift, blast percentage, basophilia, and thrombocytosis on complete blood count with differential, as recommended by the College of American Pathologists 5
Perform peripheral blood smear examination to identify blasts, dysplasia, immature granulocytes, and basophils, according to the American Society of Clinical Oncology 5
Quantify degree of splenomegaly on physical examination, and assess for hepatomegaly, as recommended by the European Association for the Study of the Liver 1, 2, 3, 7

Obtain Philadelphia chromosome testing via cytogenetics and/or BCR-ABL by RT-PCR or FISH from peripheral blood or bone marrow if CML is suspected, as recommended by the National Comprehensive Cancer Network 3
Perform bone marrow aspiration and biopsy immediately for blast percentage and dysplasia assessment if acute leukemia is suspected, according to the American Society of Hematology 5, 6

Hydroxyurea for rapid cytoreduction if symptomatic leukocytosis or massive splenomegaly is present in confirmed or suspected CML, as recommended by the European Hematology Association 5, 6
Imatinib 400 mg daily is first-line standard therapy once CML diagnosis is confirmed, according to the National Comprehensive Cancer Network 2, 3
Emergency leukapheresis is recommended for AML with symptomatic leukocytosis, as noted by the American Society of Clinical Oncology 5, 6
Start ATRA immediately if APL is suspected—do not wait for genetic confirmation, as recommended by the American Society of Hematology 5, 6