In a Phase 1 study in 15 human patients, the LUM Imaging System distinguished areas of malignant sarcoma and breast cancer from surrounding normal tissue in ex vivo surgical specimens.19 LUM015 was shown to be activated by proteases, particularly cathepsins K, L, S, and B. We recently reported the first human in vivo use of the LUM Imaging System during breast cancer lumpectomy surgery.21 Both invasive tumor and ductal carcinoma in situ (DCIS) were rapidly distinguished from normal tissue with high sensitivity and good specificity. Here, CTSK is linked to breast cancer.