Each year, thousands of dogs die of canine hemangiosarcoma (HSA), an extremely aggressive vascular cancer that arises from transformed endothelial cells or endothelial precursors of the spleen, heart, liver, and other primary locations. Approximately 65% of all diagnosed cases are splenic and this form of HSA is often first detected when the mass ruptures, causing severe life-threatening internal bleeding, lethargy, and, usually a visit to the emergency room. At this late stage of tumor progression, the cancer has often already metastasized throughout the body and the prognosis is dire. Currently, the process for determining whether a splenic mass is malignant (most commonly HSA) or benign (hematoma, lymphoid hyperplasia) is lengthy and expensive, involving splenectomy and histopathology, forcing clinicians and owners to make life and death decisions for the pet based on statistics and without accurate diagnostic information for the individual. A rapid-test Point-of-Care (PoC) device that can accurately distinguish HSA from other splenic diseases would be highly desirable as it would help to guide the clinicians and owners in their decision-making process. miRNAs are small non-coding RNAs (17–25 nucleotides) that are evolutionarily conserved, naturally abundant, and relatively stable molecules that facilitate post transcriptional gene regulation in many biological and pathological processes. Over the last decade miRNAs have been increasingly recognized as promising biomarkers for various types of cancers. Our preliminary studies have shown that serum levels of miR-132 are significantly increased (p<0.00001) while serum levels of miR-486 are significantly decreased (p<0.00001) in dogs ultimately diagnosed with HSA when compared to dogs with other diagnoses and to healthy controls. These preliminary findings suggest that miR- 132 and miR-486 represent promising new diagnostic tools for HSA. While these biomarkers may accurately differentiate HSA from benign disease, thus far, a technology that would enable rapid and clinically meaningful detection of these promising miRNAs at the PoC level is lacking. Given these observations, the goals of our collaborative project are to address this unmet need via three main objectives: 1) confirm the ability of our serum miRNA biomarkers to differentiate dogs with HSA from dogs with benign splenic masses, 2) further develop our innovative Tethered Enzyme Technology (TET) for rapid detection of these miRNAs, and 3) test the utility of our TET-based Rapid-HSA-test in a pilot clinical study at the Cornell University Hospital for Animals.