The genetic and environmental conditions that confer teratoma susceptibility in the 129/SvJ background remain poorly understood, although mutations in several genes including Dnd1 (Dead-end 1), Dmrt1 (Doublesex and mab-3 related transcription factor 1), Pten (Phosphatase and tensin homolog) and Bax (Bcl2-associated X protein) underlie increased tumour incidence [20], [21], [22], [23], [24]. The gene discussed is DND1; the disease is teratoma.