Tumors arising from the germ cells

The tumors that originate from the primordial germ cells amount to ca. 4% of all tumors in childhood. Most frequently, they appear before 3 or after 12 years of age. Two thirds are benign.

These tumors develop from the primordial germ cells (PGC) that can be detected in the epiblast following the formation of the primitive streak 6 and with an initial migration proceed extra-embryonically into the endoderm of the umbilical vesicle. From there they immigrate via the mesenterium into the genital ridge (future gonads).
This migration occurs between the 4th and 6th week (stages 11-14).
A pathologic PGC migration can lead to an ectopic localization (sacro-coccygeal, retro-peritoneal, mediastinal, intracranial and epiphyseal regions).

The germ cell tumors are classified as follows:

• Germinoma
• Embryonic tumors
• Extraembryonic tumors

This histological classification reflects the degree of differentiation that the cells have reached before they degenerate malignantly. This can happen to the cells at the following stages:

• In the germ cell stage (germinoma)
• In some stage of differentiation that has progressed further within the embryo (teratoma, embryonic carcinoma)
• In some stage of differentiation that has progressed further outside the embryo (tumors of the umbilical vesicle, choriocarcinoma)

Germinoma

Germinomas (seminoma in the testes, dysgerminoma in an ovary) represents only 15% of all germ cell tumors in children.
A seminoma is a germ cell tumor that appears more frequently with a cryptorchism or with a dysgenesis of the gonads (Klinefelter's syndrome, syndrome of the testicular feminization).

Embryonic carcinoma

An embryonic carcinoma can transform itself into a teratoma and makes up 1/3 of all testicular germ cell tumors.

Teratoma

Teratomas consist of a combination of the tissues from all three blastodermic layers (ecto-, meso- and endoderm). One distinguishes mature teratomas (cysts), immature teratomas (solid tissue) and malignantly degenerated teratomas.

In an adult woman, a complication of an ovarian teratoma is a torsion of the affected ovary with her fallopian tube.

Tumors arising from the yolk sac

Tumors of the umbilical vesicle are relatively frequent tumors in newborns.

Choriocarcinoma

Choriocarcinomas were treated in the placenta module.