Cytogenetics, ploidy and differentiation of human testicular, ovarian and extragonadal germ cell tumours

Data from cytogenetics of testicular, ovarian and extragonadal germ cell tumours indicate that the group of germ cell tumours for which Skakkebaek proposed the name gonocytoma (seminoma, dysgerminoma and germinoma) is characterized by the presence of isochromosome 12p. The (dysplastic) gonocytes from which these tumours are derived are prone to polyploidization, especially in the gonads. There is evidence that non-seminomatous germ cell tumours in the testis may evolve through a (subclinical?) gonocytoma stage by loss of chromosomes. Since gonocytomas have already acquired the i(12p) marker, evolution of non-seminomatous germ cell tumours from gonocytomas would explain the presence of i(12p) in non-seminomatous germ cell tumours of the adult testis. A similar evolution may account for the presence of i(12p) in testicular type non-seminomatous germ cell tumours occurring in the ovary and extragonadally.