Several important milestones in veterinary oncology have occurred between the publication of the third edition of the textbook in 2001 and the current edition. One in particular represents a significant loss to the community and indeed this publication; the passing of E. Gregory MacEwen. Greg was a pioneering leader in the field of veterinary oncology and was responsible for the development of several novel and innovative cancer therapies for both companion animals and people. Invariably those of us that were touched by him professionally also developed a deep and heart-felt personal relationship with this kind and gentle man. His untimely passing left a tremendous void; however, he continues to serve as an inspiration to those in the field, and the work that he initiated continues to advance the art and science of oncology, in no small part due to the scores of veterinary students, residents, and post graduate students Greg educated and inspired.

During the planning of this edition, we made the decision to produce a book that was clinically relevant for the general practitioner and veterinary medical student as well as being a state-of-the-art text with an emphasis on the molecular basis, biologic behavior, and treatment of cancer in small animals. The fourth edition follows a similar format as the first three editions. We begin with introductory chapters on the biology and pathogenesis of cancer and follow with a section of chapters on the diagnosis and staging of the cancer patient. A general section covering the varied therapeutic modalities available to the cancer patient is then followed by a section outlining specific malignancies encountered in small animal veterinary patients; their etiology, presentation, diagnosis, therapy, and prognosis. 

All chapters have been extensively reworked and revised, and the addition of color to the current edition has an immediate impact on the aesthetics of the overall work. Care has been taken to include therapy protocols that have been evaluated with sufficient case material to allow a determination of efficacy. Noteworthy additions to the current edition include chapters on the Etiology of Cancer, Molecular Diagnostics, Molecular Targeted Therapy, and Supportive Cancer Care. We are delighted at the exceptional quality of the chapters our invited authors produced. We are particularly pleased with our publisher, Elsevier. We especially want to thank Tony Winkel, our editor, and Shelly Stringer, Developmental Editor, of the Elsevier staff. We also want to thank Rich Barber, production Manager, and Jennifer Hong, editorial assistant, for their detail in editing the typed manuscript. Special thanks are extended to Carol Horner at the Animal Cancer Center at Colorado State University for clerical and transcription services.