Germ cell tumors are infrequent tumors in childhood and adolescence.
These neoplasms comprise 2% to 3% of all tumors
diagnosed in children and adolescents ages 0 to 15 years,1 with
an annual incidence of approximately 3 per million. Extracranial
germ cell tumors are more common in adolescents 15 to 19 years of
age, accounting for 16% of cancer diagnoses in this age
group (Fig. 459-1). Ninety percent of germ
cell tumors diagnosed during adult life are gonadal, whereas two
thirds of childhood germ cell tumors are extragonadal. The age distribution
for childhood germ cell tumors is bimodal, with a peak at 3 years
of age and a second peak during adolescence. One third of germ cell
tumors of childhood are malignant, but most neonatal germ cell tumors,
irrespective of location, are benign. However, despite the relative
infrequency of malignant tissue, there is a high associated morbidity
due to obstruction of airway, hydrops fetalis, and premature delivery.2,3 With
advancing age, the proportion of malignant germ cell tumors increases.
Germ cell tumors (GCT) in children and adolescents.
Germ cell tumors are thought to develop from a common primordial
or embryonic germ cell.4 However, there is great heterogeneity
in location, histopathology, and genetics.5,6 Tumor development
is not well understood but may be related to the stage of germ cell
development, the location of stem cells at time of tumorigenesis,
and the sex of the individual. During normal development, primordial
germ cells migrate from the yolk sac through the mesentery to the
gonadal ridge.7 The c-kit receptor and its ligand, stem
cell factor-8, have been shown to affect primitive germ cell directional
migration to the gonadal ridge. Extragonadal germ cell tumors may
develop from primordial germ cells that display an abnormal migration
Germ cells may give rise to tumors at any point in their migration
path or at any stage of differentiation. The pluripotential cells
can differentiate into various embryonic or extraembryonic tissues,
which can be either benign or malignant. A mixture of benign and
malignant components is common in germ cell tumors, lending support
to the notion that different classes of germ cell tumors have a
common progenitor. Although there is little doubt that gonadal germ
cell tumors are derived from pluripotent descendants of activated
germ cells, the origin of extragonadal germ cell tumors is controversial.
Cytogenetic studies suggest that such extragonadal tumors may arise
from either misplaced pluripotent embryonic tissue or activated
A classification of pediatric germ cell tumors is shown in Table 459-1. Germ cell tumors can be classified
into mature or immature teratomas and malignant germ cell tumors.
Table 459-1. Germ
Cell Tumor Histology
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