The following genes with an identifier have been found but that do not have a mapping to Ensembl: 3
http://classic.wikipathways.org/instance/WP252_r140554 Hmg1l1 with datasource Entrez Gene
http://classic.wikipathways.org/instance/WP252_r140554 RAS with datasource Entrez Gene
http://classic.wikipathways.org/instance/WP252_r140554 Gm13882 with datasource Entrez Gene
More details at https://www.wikipathways.org/WikiPathwaysCurator/GeneTests/genesWithoutEnsemblMapping