IBCL-324: Hairy Cell Leukemia in the Era of Targeted Therapy: A Case Presentation

Context: Hairy cell Leukemia (HCL), a chronic B-cell neoplasm, accounts for 2% of all leukemias, mainly of males in their 50s. Diagnosis relies on morphology, flow cytometry, and immunohistochemistry. Purine analogues are first-line therapy since more than 20 years ago. Strategies such as combined chemoimmunotherapy, targeted therapy, and minimal residual disease (MRD) are taking over the landscape of HCL. Patient: A 47-year-old man presents with weakness, respiratory infections, pancytopenia, and a 19-cm spleen. Peripheral blood revealed mononuclear cells with hairlike projections, monocytopenia, and thrombocytopenia. Misdiagnosis of splenic lymphoma 2 years earlier had been managed with bendamustin and rituximab in a different center, having resulted in normalization of counts. At our assessment, his immunophenotype showed CD103/CD123/CD25/CD11c in 63% of cells, diagnostic of relapsed HCL. Interventions: Cladribine was initiated at 0.14 mg/kg/d, 2 h infusion for 5 days, and supportive measures. At 3 months, MRD was negative; 28 months later, he remains in remission. Results: Molecular identification of somatic BRAFV600 mutation is diagnostic, as well as an effective therapeutic target. MRD is thought to predict late relapse in HCL and select patients to benefit from additional or further treatment. Monoclonal antibodies anti-CD20 and anti-CD22 Moxetumomab have proven safe and efficacious in treating HCL. Conclusions: Hairy cell Leukemia is a rare hematologic malignancy that can be confused with other indolent lymphoid malignancies. Current treatment is effective, but clinical trials are needed to develop best practices to offer patients with HCL a normal life expectancy.