DKK2 gene amplification and homozygous deletion are rare in prostate cancer, with gene amplification being slightly more frequent in metastatic cases (primary: 0–0.7% and 0.3–0.4% respectively, metastatic: 1.4–1.8% and 0–0.7% respectively, Tables S1–S4) [64,65,66]. The gene discussed is DKK2; the disease is prostate cancer.