The new WHO classification of B-cell neoplasms published in 2001 gathers leukaemia and lymphoma. This classification highlights the stage of differentiation of the tumour cell. It groups B-cell neoplasms morphology, histology (nodular or diffuse pattern, cell morphology), immunophenotypes, cytogenetic, molecular abnormalities and clinical data. Recent advances of the normal B cell differentiation understanding and the development of new types of analysis have shown that mature B-cell neoplasms appear to recapitulate stages of normal B-cell differentiation, leading to such a new classification.