PROS1 and prostate cancer: For each patient in each group (i.e., BPH, “low severity” prostate cancer, and “high severity prostate cancer”), the corresponding serum ferritin level was then calculated and plotted against tissue ferritin staining grade (0, 1, 2, or 3) in a bubble plot, with the size of each bubble corresponding to that patient's total PSA level (Figure 3B).