CTSB and ductal breast carcinoma in situ: Recently, CSTA, a protease inhibitor of cathepsin B activity, was found to be downregulated in invasive carcinomas adjacent to DCIS.40 Surprisingly, we found high levels of CSTA expression in DCIS to be associated with micro invasion, which is somewhat contradictory with the initial finding of Lee et al.40 who found that down regulation of CSTA was associated with progression of DCIS to invasive carcinoma.