This issue of Hematology/Oncology Clinics, Guest Edited by Dr. John P. Leonard, is devoted to Mantle Cell Lymphoma. This issue is one of six selected each year by our series Consulting Editors, George P. Canellos and Edward J. Benz. Topics discussed in this important issue include: Molecular pathogenesis of Mantle Cell Lymphoma; MCL and cell cycle dysregulation; Heterogeneity in MCL biology and outcomes; Watch and wait in mantle cell lymphoma; Limited stage mantle cell lymphoma; Initial and consolidation therapy for younger patients with MCL; Approach to the initial treatment of older patients with MCL; Current and future approaches to the use of minimal residual disease monitoring in the treatment of patients with MCL; Bruton's Tyrosine Kinase inhibitors for treatment of Mantle Cell Lymphoma; BTKi resistance in MCL; Blastoid MCL; Allogeneic transplant and CAR-T cell therapy in MCL; Quality of life considerations and chronic therapy in management of patients with MCL; and Key clinical and translational research questions.