Why are ovarian teratomas benign whilst teratomas of the testis are malignant?

A mechanism is suggested to account for the fact that most ovarian teratomas are benign (dermoid cysts) whereas testicular teratomas are almost always malignant. The mechanism advanced assumes that malignancy is cause by a recessive mutation, and then shows that the known facts of germ-cell development will produce the homozygous (malignant) state in the male but the heterozygous counterpart in the female. It is proposed that the benign nature of ovarian teratomas is a reflection of this heterozygous genotype.