The merging of different basic and clinical science disciplines towards the common goal of fighting against cancer has long ago called for the establishment of a comprehensive reference source both as a tool to close the language gap between clinical and basic science investigators and as a platform of information for students and informed laymen alike. The Encyclopedia of Cancer provides rapid access to focused information on all topics of cancer research for clinicians, research scientists and advanced students. Given the overwhelming success of the Second Edition, which appeared in 2009, and fast recent development in the different fields of cancer research, it has been decided to publish a third fully revised and expanded edition, following the principal concept of the first edition that has proven so successful. Recent developments are seeing a dynamic progress in basic and clinical cancer science, with translational research increasingly becoming a new paradigm in cancer research. In particular, new approaches to both Personalized Cancer Medicine and Targeted Therapies have made promising progress. While the Second Edition featured scholarly contributions from approximately 1.000 scientists/clinicians in four Volumes, the Third Edition includes 1.300 contributors in 7 Volumes with an A-Z format of approx. 7000 entries. It provides definitions of common acronyms and short definitions of related terms and processes in the form of keyword entries. In addition, there are detailed essays, which provide comprehensive information on syndromes, genes and molecules, and processes and methods. Each essay is well-structured, with extensive cross-referencing between all entries. In the Third Edition, topical Essays present a comprehensive picture of major cancers, such as Breast Cancer, Colorectal Cancer, Prostate Cancer, Ovarian Cancer, Renal Cancer, Lung Cancer, and Hematological Maligancies, Leukemias and Lymphomas. For each of these cancers, different authoritative  Essays are included that cover topics ranging from Pathology, to Clinical Oncology and Targeted Therapies. This new feature should meet the expectance that a wide community has towards a major cancer reference works. The Encyclopedia of Cancer will be accessible both in print and online, and this information source should be of value to both the clinical and basic scientific community as well as to the public.