The systematic literature search yielded a total of 33 studies including a total of 4801 subjects (2238 patients with lung cancer and 2563 controls) and covering 32 genes (P16, RASSF1A, APC, MGMT, PAX5, CGB, GATA, DAPK, RARβ, MAGE, HOXA, 3OST2, PRDM14, FAM19A4, PHACTR3, PCDH20, CXCL, Dal-1, Dab2, Dcr2, SULF2, Kifla, Jph3, SOX17, CDO1, ZFP42, TAC1, CDH1, H-cadherin, FHIT, RASSF2, TCF2l). The gene discussed is PCDH20; the disease is lung cancer.