KLK4 and prostate intraepithelial neoplasia: In prostatic intraepithelial neoplasia (PIN) lesions, KLK4 staining was strong and predominantly localized to the cytoplasm of the secretory cells of prostate glands (Fig. 1Aa–c), and the basal cells of low‐ and high‐grade PIN lesions (LGPIN, HGPIN, closed arrows, Fig. 1Ab–c).