CSTB and ovarian cancer: It was shown in the presented work that compared to serum of the control group, the increase in procathepsin B concentration (p<0.001,13-fold elevation) in ascites of patients with ovarian cancer was the highest; with cystatin C being the second highest (p<0.05, elevation about 1.8-fold) and cystatin B the third highest (p<0.001, increased up to 1.4-fold).