Experimental production of testicular teratomas in the mouse.

Testicular teratomas are congenital tumours that are extremely rare in mice except for the inbred strain 129 and strains derived from it. A third of the males of strain 129/Sv-ter has spontaneous teratomas. Teratomas may be easily produced experimentally in some inbred strains and hybrids by grafting genital ridges from male foetuses 12 days of gestation to scrotal adult testes. The grafted genital ridges develop into well formed testes and most of them have teratomas composed of many kinds of well differentiated tissues derived from all 3 germ layers. Experimentally induced teratomas may be recognized as early as six days after grafting when they are composed of small clusters of embryonal carcinoma cells. The low temperature of the scrotal testis is a critical factor in experimental teratocarcinogenesis. When genital ridges from genetically sterile (S1/S1) foetuses that lack germ cells are grafted, they develop into testes without teratomas whereas grafts from testes that develop from their normal littermates do have teratomas. This demonstrates that testicular teratomas are derived from primordial germ cells.