KLK3 and metastatic malignant neoplasm: Through binding to PSMA, a transmembrane protein expressed predominantly in prostate cells and especially in prostate cancer cells, 68Ga-PSMA leads to the internalization and accumulation in primary and metastatic cancer lesions (90), which is proven to have the higher yield of positive scans than obtained with other tracers at a low PSA level (91, 92).