KLK3 and neoplasm: In this metastasis cohort, the mean PSA staining score of tumor epithelial cells was 7 (median 6, Q1 4, Q4 10, range 1–12, n = 164) and the mean Ki67 + fraction was 20% (median 16, Q1 9, Q4 26, range 1–80, n = 162), indicating substantial variability between patients (Supplement Fig. 1).