Since the third edition of Tumors of Domestic Animals there has been an enormous expansion of our knowledge about the melocular mechanisms of tumor development and the ancillary aids used diagnose neoplasms . The fourth edition condenses this new body of information and presents it in a way that is useful to diagnostic pathologists, residents, veterinarians, and oncologists. The format of the previous editions has been maintained, but the text and the illustrations are substantially changed or entirely different. Readers will be able to find salient clinical information, prevalence data, biological behavior, and most importantly, accurate information about gross and microscopic lesions to help diagnostic pathologists establish an accurate morphological diagnosis. The editor and authors of Tumors of Domestic Animals,all recognized experts in their fields, recognize the need for accurate morpological diagnoses in veterinary patient care, particularly with the numerous treatment modalities now available to oncologists and owners. This landmark reference in veterinary pathology provides the applicable information that clinical veterinarians need and want to make decisions about treatment of the animals in their care.