THE BIOLOGY OF TERATOMAS
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metabolites available. The degree of organization from highly organized
to amorphous, was induced by manipulation of the culture medium on
which the tumor is grown.
XV. Summary
Embryonal carcinomas are tumors of germ cell origin composed of
undifferentiated embryonal-type cells. Some of these cells may differentiate, giving rise to teratocarcinomas composed of both embryonal
and mature tissue. All of the embryonal cells may differentiate and form
teratomas. The term teratoma is used here to include all three varieties.
Teratomas occur in man, horses, guinea pigs, fowl, and mice. They are
common only in inbred strain 129 mice. The growth and differentiation
of teratomas is influenced by the sex of the bearer and laterality. They
may be simple in composition, or they may be composed of almost all
kinds of tissues, depending upon the embryonic potency of the stem
cell which may change. This change may result in a more or less malignant tumor, and the stem cell may become determined so that only yolk
sac, myoblastic, or neural tissues are produced.
Teratomas are derived from germ cells, and those of strain 129 mice
are derived from primordial germ cells. Extragonadal teratomas are rare
and they are thought to be derived from germ cells that become misplaced during their migration from the yolk sac to the genital ridge
during fetal life. In strain 129 mice, teratocarcinogenesis is initiated
in the primordial germ cells at 12.5 days of gestation. They proliferate
and give rise to nests of pluripotent embryonal cells. These nests grow,
rupture the seminiferous tubules in which they arise, and spill out into
the interstitial area. The first sign of differentiation is the formation of
vesicles lined by epithelium. Some of the epithelium transforms into
ectoderm, and some into endoderm. Other cells, between the epithelial
vesicles are mesodermal. The three primary germ layers give rise to all
of the mature tissues of the teratomas.
Some teratomas of the mouse grow progressively and can be indefinitely serially transplanted. The stem cell of some of these tumors is a
pluripotent embryonal-type cell.
The susceptibility to teratocarcinogenesis in mice is the result of the
action of a single major gene. The penetrance of this gene is modified
in both positive and negative directions by other genes. Local environmental influences such as cryptorchidism and laterality influence the
incidence of teratomas. There is also a maternal influence. There are no
gross chromosomal abnormalities in early testicular teratomas of mice,
and they have the Y chromosome which means they are male. Testicular
teratomas have been found to contain sex chromatin in some humans,
27
metabolites available. The degree of organization from highly organized
to amorphous, was induced by manipulation of the culture medium on
which the tumor is grown.
XV. Summary
Embryonal carcinomas are tumors of germ cell origin composed of
undifferentiated embryonal-type cells. Some of these cells may differentiate, giving rise to teratocarcinomas composed of both embryonal
and mature tissue. All of the embryonal cells may differentiate and form
teratomas. The term teratoma is used here to include all three varieties.
Teratomas occur in man, horses, guinea pigs, fowl, and mice. They are
common only in inbred strain 129 mice. The growth and differentiation
of teratomas is influenced by the sex of the bearer and laterality. They
may be simple in composition, or they may be composed of almost all
kinds of tissues, depending upon the embryonic potency of the stem
cell which may change. This change may result in a more or less malignant tumor, and the stem cell may become determined so that only yolk
sac, myoblastic, or neural tissues are produced.
Teratomas are derived from germ cells, and those of strain 129 mice
are derived from primordial germ cells. Extragonadal teratomas are rare
and they are thought to be derived from germ cells that become misplaced during their migration from the yolk sac to the genital ridge
during fetal life. In strain 129 mice, teratocarcinogenesis is initiated
in the primordial germ cells at 12.5 days of gestation. They proliferate
and give rise to nests of pluripotent embryonal cells. These nests grow,
rupture the seminiferous tubules in which they arise, and spill out into
the interstitial area. The first sign of differentiation is the formation of
vesicles lined by epithelium. Some of the epithelium transforms into
ectoderm, and some into endoderm. Other cells, between the epithelial
vesicles are mesodermal. The three primary germ layers give rise to all
of the mature tissues of the teratomas.
Some teratomas of the mouse grow progressively and can be indefinitely serially transplanted. The stem cell of some of these tumors is a
pluripotent embryonal-type cell.
The susceptibility to teratocarcinogenesis in mice is the result of the
action of a single major gene. The penetrance of this gene is modified
in both positive and negative directions by other genes. Local environmental influences such as cryptorchidism and laterality influence the
incidence of teratomas. There is also a maternal influence. There are no
gross chromosomal abnormalities in early testicular teratomas of mice,
and they have the Y chromosome which means they are male. Testicular
teratomas have been found to contain sex chromatin in some humans,