Recently, assays have incorporated cathepsins B, D, G, K, L, V and S quantification using IHC (from BC patients [73]), RT-PCR, Western analysis, reverse-phase protein arrays (from acute lymphoid leukemia patients, ALL [74]), cathepsin expression levels and activity analysis (from acute myeloid leukemia patients, AML [75]), in silico analysis and histological staining (from papillary thyroid cancer patients [76] and esophageal cancer patients [51]). The gene discussed is CTSS; the disease is breast cancer.