Hormones and growth factors in germ cell neoplasia: general discussion.
Fetal germ cells migrate along the dorsal mesentery to the genital ridge, and migration in the bloodstream occurs in some animals. Malignant transformation may occur before migration, and it is possible that testicular germ cell tumours have a monoclonal origin, even when bilateral. Different tumour foci have homogeneous chromosomal abnormalities. Migrating germ cells may lodge in extragonadal sites and give rise to tumours. Mouse fetuses exposed to oestrogen and testosterone in utero have an increased incidence of testicular maldescent and teratoma. Oestrogens and mullerian inhibitory substance in the fetus may influence human testicular tumour development. Testicular tumour patients may have elevated serum oestrogen levels which may be related to prognosis. Increased serum FSH may stimulate germ cell tumour growth. Ultrastructural studies indicate that malignant transformation of germ cells occurs early, but final tumour differentiation does not occur till after the malignant cells have invaded extratubular tissue.