Mantle cell lymphoma (MCL) is a B-cell non-Hodgkin lymphoma (NHL) and it accounts for about 6% of all NHL cases. Diagnosis is based on lymph node, bone marrow, or tissue morphology of centrocytic lymphocytes, small cell type, or blastoid variant cells. The molecular hallmark and putative initiating oncogenic event in MCL is the t(11;14)(q13;q32) translocation resulting in constitutional overexpression of cyclin D1 and cell cycle dysregulation in almost all cases. Clinically, MCL shows an aggressive clinical course with a continuous relapse pattern and a median survival of only 3-5 years. However, recently a subset of 15% long-term survivors has been identified with a rather indolent clinical course.