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Relapsed Refractory BRAF-Negative, IGHV4-34-Positive Variant of Hairy Cell Leukemia: A Distinct Entity?

Case Report A 69-year-old woman presented to us in January 2013 with progressive fatigue, weight loss of 30 pounds in the last 2 years, and shortness of breath on exertion. She presented to an outside hospital in March 2010 with similar complaints and was found to have pancytopenia; bone marrow (BM) examination revealed hairy cell leukemia (HCL), and she was treated with single-agent cladribine given by continuous infusion for 7 days. Her blood counts improved, but a BM examination to assess response was not performed. In July 2010, her counts declined again, and a repeat BM examination showed persistent HCL. She received a second course of cladribine over 7 days and had improvement in counts without achieving complete remission. She experienced relapse a year later and underwent a splenectomy in January 2011. She did not have a response to splenectomy and received four weekly doses of singleagent rituximab in March 2012 without significant improvement in her counts. In July 2012, she was started on thrice-weekly interferon therapy together with twice-weekly granulocyte colonystimulating actor without a response and was then referred to our institution for further evaluation. Her physical examination was unremarkable except for a palpable 2-cm right-side submandibular lymph node, multiple subcentimeter-size lymph nodes in bilateral cervical and axillary regions, as well as a palpable 2-cm left axillary lymph node. Investigations showed hemoglobin of 9.6 g/dL, white cell count of 2.8 K/ L, hematocrit of 28.8%, and platelet count of 41 K/ L. Differential count was normal except for mild neutropenia with an absolute neutrophil count of 1.46 K/ L. Peripheral blood smear demonstrated pancytopenia. Lymphocytes were relatively increased and demonstrated light basophilic cytoplasm with hairy cell cytoplasmic projections. Her renal and hepatic functions were normal except for mildly elevated enzymes, AST (105 IU/L; normal range 15-46), and ALT (136 IU/L; normal range 7-56) and ALP (500 IU/L; normal range 38-126). Serum immunoglobulin levels were normal. Serum 2 microglobulin was 4.7 mg/L (normal range 0.8-2.3). Serum interleukin-2 receptor levels were more than 6,500 units/mL (normal being 970 units/ mL). An x-ray of the chest was normal. BM aspirate showed 86% lymphocytes with multiple hairy cells with circumferential cytoplasmic projections and kidney-shaped nuclear contours. Tartrateresistant acid phosphatase (TRAP) stain was positive (Figs 1A to 1B; 1,000 magnification). Flow cytometry studies of the BM aspirate