Hairy cell leukemia variant in a patient with chronic myeloid leukemia receiving nilotinib: sequential or coincidental?

Recommendations of the SFH (French Society of Haematology) for the diagnosis, treatment and follow-up of hairy cell leukaemia

Hairy cell leukaemia (HCL) is a rare haematological malignancy, with approximately 175 new incident cases in France. Diagnosis is based on a careful examination of the blood smear and immunophenotyping of the tumour cells, with a panel of four markers being used specifically to screen for hairy cells (CD11c, CD25, CD103 and CD123). In 2011, the V600E mutation of the BRAF gene in exon 15 was identified in HCL; being present in HCL, it is absent in the variant form of HCL (HCL-v) and in splenic red pulp lymphoma (SRPL), two entities related to HCL. The management of patients with HCL has changed in recent years. A poorer response to purine nucleoside analogues (PNAs) is observed in patients with more marked leukocytosis, bulky splenomegaly, an unmutated immunoglobulin variable heavy chain (IgVH) gene profile, use of VH4–34 or with TP53 mutations. We present the recommendations of a group of 11 experts belonging to a number of French hospitals. This group met in November 2013 to examine the criteria for managing patients with HCL. The ideas and proposals of the group are based on a critical analysis of the recommendations already published in the literature and on an analysis of the practices of clinical haematology departments with experience in managing these patients. The first-line treatment uses purine analogues: cladribine or pentostatin. The role of BRAF inhibitors, whether or not combined with MEK inhibitors, is discussed. The panel of French experts proposed recommendations to manage patients with HCL, which can be used in a daily practice.

De novo hairy cell leukemia with a major BCR/ABL1 rearrangement: a case report with a literature review

Hairy cell leukemia (HCL) is a very rare mature B-cell neoplasm and its simultaneous occurrence with chronic myeloid leukemia has been reported in only three cases. The pathogenesis and relationship of the two diseases are not clear. Here we report a case of HCL expressing a BCR/ABL1 clone, which showed molecular remission of the fusion clones and achieved partial remission over nine months of cladribine therapy. After a thorough analysis of previous studies and the results of this patient, we speculate that a subclone evolved to have an additional genetic BCR/ABL1 rearrangement. We also review all published literature on HCL with BCR/ABL1 rearrangement and discuss the pathophysiology of these unusual cases.