Secondary T-lymphoblastic leukemia in a patient with hairy cell leukemia following cladribine therapy: report of an extremely rare case and review of the literature

Abstract

Hairy cell leukemia, a rare B-cell lymphoproliferative neoplasm, accounts for about 2% of all leukemias. Bone marrow and spleen are typical sites of involvement. Patients most commonly present with splenomegaly and pancytopenia and a few circulating small- to medium-sized lymphoid cells with circumferential hairy projections (hairy cells). For years the common approach to treatment of hairy cell leukemia was splenectomy and α -interferon; complete remission was not easily reachable, and median survival was only 4 years. In the 1980s, with the introduction of the purine analogs pentostatin (2-deoxycoformycin) and cladribine (2-chlorodeoxyadenosine), the treatment strategy dramatically changed, resulting in improved prognosis for those with the disease. With these treatments, follow-up studies on patients with hairy cell leukemia showed a higher overall complete remission rate, ranging from 76 to 98%, and a prolonged median disease-free survival of 11 – 16 years [1]. However, an adverse outcome encountered in hairy cell leukemia aff ecting the overall survival is the subsequent development