Sarcomas are malignant cancers that can arise in any part of the body; however, in the dog a subset referred to as soft tissue sarcomas account for 10-15% of all skin and subcutaneous cancers.  Traditionally biopsy and subsequent histology has been the primary means of diagnosing these cancers.  The histology is assigned to one of three grades ranging from low (grade I), intermediate (grade II), and high (grade III).  Currently histologic grade is the key criterion for guiding treatment and determining patient outcome.  However, in human medicine and pathology, soft tissue sarcomas are diagnosed with a hybrid approach that involves both histologic features and genetic analysis of the tumor sample.  This genetic analysis guides further treatment, aids in developing accurate follow-up information, and has been shown to have a positive effect on patient outcome and survival.  Unfortunately, despite how common soft tissue sarcomas are in the dog, we still rely solely on the histologic grade, which is subjective at best, and we do not incorporate any genetic data into our diagnostic plan.  The objective of this grant is to develop a validated test to analyze the genes present in canine soft tissue sarcoma. This will allow for future prospective studies in which genetic analysis will be used to guide treatment in dogs afflicted with this cancer, lead to more refined care, and ultimately improve patient outcome.