This probe was intravenously injected in breast cancer bearing mice, and the non-invasive, whole-body imaging allowed the direct monitoring of cathepsin activity in tumor and spleen, kidneys and liver (all organs where cathepsins B and L were expressed), and showed no background since the earliest time point (conversely, the use of the same probe without the quencher resulted in a general background until 12 hours after injection). This evidence concerns the gene CTSS and neoplasm.