Hairy Cell Leukemia

Hairy cell leukemia is a rare, indolent, chronic lymphoid neoplasm originating from a mature B lymphocyte. Diagnosis is based on hairy cell morphology, immunological phenotype by flow cytometry and/or immunohistochemistry in trephine biopsy, and the presence of BRAFV600E somatic mutation. In the classic form of the disease, the purine nucleoside analogues pentostatin and cladribine are recommended for the first-line treatment. These agents induce durable and unmaintained complete response in more than 70% of cases and up to 35% of patients demonstrate overall survival longer than 20 years. When rituximab is combined with cladribine in early relapse, complete response can be achieved in 89–100% of patients, with a three-year risk of relapse of only 7%. More recently, several new drugs have been introduced for the treatment of patients with hairy cell leukemia. Clinical trials have confirmed that the immunotoxin moxetumomab pasudotox, BRAF kinase inhibitors (vemurafenib and dabrafenib), and the Bruton kinase inhibitor ibrutinib are useful agents in the treatment of patients who are refractory to purine analogs.