Fen1+/− mice (Fen1 KO is embryonically lethal [130]) have an increased risk of tumour development, especially lymphomas [131], and tumorigenesis is further increased in combination with other alterations such as Apc1638N; these mice present reduced survival and increased intestinal adenocarcinomas compared to Apc1638N alone [131]. The gene discussed is FEN1; the disease is neoplasm.