My goal for this textbook is to provide an overview of the discipline of hematopathology that connects the field with recent advances in immunology research and with current clinical practice in the treatment of lymphomas and leukemias. With separate sections on laboratory techniques, diagnostic hematopathology, treatment, and stem cell transplantation, this book is designed to be useful for both trainees and specialists in pathology and hematology-oncology. We have also summarized the current directions in translational research that will be of most interest to experienced hematopathologists and scientists working in lymphoma and leukemia biology.