Cancer, Leukemia, Hairy Cell

Hairy cell leukemia (HCL) is a relatively rare chronic B-cell malignancy that involves the bone marrow, spleen, and peripheral blood. The complete blood count may reveal pancytopenia including monocytopenia. Median age at diagnosis is approximately 55. Poor prognostic features, while somewhat variable in the literature, may include age, hemoglobin less than 10 g/dL, platelets less than 100, ANC less than 1000, the presence of lymphadenopathy, and massive splenomegaly. Differential diagnosis includes other B-cell lymphoproliferative disorders, including splenic marginal zone lymphoma. A distinct entity is known as hairy cell leukemia variant (HCL-V), which is biologically unique from HCL also exists. Response to typical HCL in this disease is poor. The variant can be identified by immunophenotypic differences, lack of BRAF mutation, and lack of monocytopenia.[1][2] HCL accounts for 2% of all leukemias with approximately 1000 new cases being reported in the United States each year.