The following genes with an identifier have been found but that do not have a mapping to Ensembl: 2
http://classic.wikipathways.org/instance/WP2877_r119905 DEFB109C with datasource Entrez Gene
http://classic.wikipathways.org/instance/WP2877_r119905 MEG8 with datasource Entrez Gene
More details at https://www.wikipathways.org/WikiPathwaysCurator/GeneTests/genesWithoutEnsemblMapping