Extragonadal Germ Cell Tumors What Is It? Extragonadal germ cell
tumors are made up of cells that form during the early
development of a fetus (unborn baby). In a growing fetus, germ
cells typically move from a site near the middle of the body to
the ovaries or testes (gonads). There they develop into eggs in
females and sperm in males. When cells that are meant to form
sperm or eggs travel to other parts of the body instead, they
can form tumors outside the gonads. That's why they are often
called extragonadal germ cell tumors. They usually begin in the
lungs; the lower back; the back of the abdomen; or the middle of
the brain, near the pea-sized pineal gland. Extragonadal germ
cell tumors (EGCTs) are rare. EGCTs are classified as seminomas
or nonseminomas (of which there are several subtypes). In
children, EGCTs affect boys and girls equally. But in adults,
the vast majority of these tumors affect men. The cells of each
type of tumor look different under a microscope. Also, each has
a different prognosis an