[Hairy cell leukemia].

Hairy cell leukemia (HCL) is a well-defined entity. Proliferation with hair cells, morphological aspects of hairy cells are easy to identify. Hairy cells express markers CD11c, CD25, CD103 and CD123. In 80% of cases, a BRAFV600E mutation is highlighted. In the absence of a BRAFV600E mutation, the differential diagnosis with other hair cell proliferations can be difficult, especially with the variant form of hairy leukemia, diffuse lymphoma of the red pulp of the spleen or splenic lymphoma of the marginal zone. Purine analogues (PNA) with or without anti-CD20 antibodies remain the first-line reference treatment. In case of relapse or resistance to PNA, BRAF inhibitors, with or without MEK inhibitors, are proposed in patients with the mutation. In the absence of BRAFV600E mutation, moxetumomab-pasudotox represents an interesting alternative. A multidisciplinary discussion is always necessary. In complex cases, expert advice is desirable.