s
L E R O Y C. S T E V E N S
were not positively identified, but the gonad was well organized. It is
emphasized that this is an exceptional case. The author does not know
of any other example of gonadal tissue in a teratoma.
Teratomas are a chaotic mixture of tissues lacking organization, but
some tissue associations exist. Skin with hair, pigment cells, and sebaceous
glands are occasionally seen in mouse teratomas. Muscle is frequently
attached to cartilage and bone, and intestinal epithelium surrounded by
a two-layered muscle coat is not uncommon (Stevens and Hummel,
1957). Nicholsen (1929) made the remarkable discovery that the sensory
nerves of the skin of a sacrococcygeal teratoma came from the sacral
nerves of the patient. Coutelle (1961) described the innervation of
teratomas and found that nerves of the host may form synapses with
ganglia of the teratoma.
It will be seen below that the histogenetic capacity of a teratoma is a
direct reflection of the embryonic potency of its stem cell.
V. Nature of the Stem Cell
All of the immature and adult-type cells in teratomas are derived from
undifferentiated pluripotent embryonal cells. Some of the evidence supporting this conclusion is indirect. Transitional stages between undifferentiated embryonal cells through immature forms to adult cells have
been observed in human and mouse teratomas (Jackson and Brues,
1941 ; Fekete and Ferrigno, 1952).
Experimental evidence using induced tumors of the fowl and primary
and transplanted teratomas of strain 129 mice has strongly supported the
conclusion that differentiated elements in teratomas are derived from
pluripotent undifferentiated cells (Carleton et al., 1953; Pierce et al.,
1959a, 1960, 1961; Stevens 1959, 1960). Carleton et al. (1953) examined
testes of fowl for varying periods after induction of teratomas by zinc
salts, and they found that the early tumors were composed of undifferentiated cells. Tumors in testes examined after longer exposure to
zinc salts contained many types of differentiated cells, obviously derived
from the undifferentiated cells observed in early tumors.
Teratomas in fetal mice are composed entirely of undifferentiated
embryonal cells, and the tumors become more complex histologically as
the animals age (Stevens, 1962). It is obvious that the differentiated
cells in the older tumors were derived from the undifferentiated embryonal cells.
Pierce et al. (1959a, 1960) and Stevens (1960) grafted embryoid
bodies, some composed of only endoderm and undifferentiated cells,
subcutaneously and into the anterior chamber of the eye of adults and
obtained growths of many differentiated cell types. These observations
demonstrated that adult-type tissues in teratomas of the mouse are
L E R O Y C. S T E V E N S
were not positively identified, but the gonad was well organized. It is
emphasized that this is an exceptional case. The author does not know
of any other example of gonadal tissue in a teratoma.
Teratomas are a chaotic mixture of tissues lacking organization, but
some tissue associations exist. Skin with hair, pigment cells, and sebaceous
glands are occasionally seen in mouse teratomas. Muscle is frequently
attached to cartilage and bone, and intestinal epithelium surrounded by
a two-layered muscle coat is not uncommon (Stevens and Hummel,
1957). Nicholsen (1929) made the remarkable discovery that the sensory
nerves of the skin of a sacrococcygeal teratoma came from the sacral
nerves of the patient. Coutelle (1961) described the innervation of
teratomas and found that nerves of the host may form synapses with
ganglia of the teratoma.
It will be seen below that the histogenetic capacity of a teratoma is a
direct reflection of the embryonic potency of its stem cell.
V. Nature of the Stem Cell
All of the immature and adult-type cells in teratomas are derived from
undifferentiated pluripotent embryonal cells. Some of the evidence supporting this conclusion is indirect. Transitional stages between undifferentiated embryonal cells through immature forms to adult cells have
been observed in human and mouse teratomas (Jackson and Brues,
1941 ; Fekete and Ferrigno, 1952).
Experimental evidence using induced tumors of the fowl and primary
and transplanted teratomas of strain 129 mice has strongly supported the
conclusion that differentiated elements in teratomas are derived from
pluripotent undifferentiated cells (Carleton et al., 1953; Pierce et al.,
1959a, 1960, 1961; Stevens 1959, 1960). Carleton et al. (1953) examined
testes of fowl for varying periods after induction of teratomas by zinc
salts, and they found that the early tumors were composed of undifferentiated cells. Tumors in testes examined after longer exposure to
zinc salts contained many types of differentiated cells, obviously derived
from the undifferentiated cells observed in early tumors.
Teratomas in fetal mice are composed entirely of undifferentiated
embryonal cells, and the tumors become more complex histologically as
the animals age (Stevens, 1962). It is obvious that the differentiated
cells in the older tumors were derived from the undifferentiated embryonal cells.
Pierce et al. (1959a, 1960) and Stevens (1960) grafted embryoid
bodies, some composed of only endoderm and undifferentiated cells,
subcutaneously and into the anterior chamber of the eye of adults and
obtained growths of many differentiated cell types. These observations
demonstrated that adult-type tissues in teratomas of the mouse are