Germ cell tumors (Pediatric)
What are germ cell tumors?
Germ cells tumors are malignant (cancerous) or nonmalignant (benign, noncancerous) tumors that are comprised mostly of germ cells. Germ cells are the cells that develop in the embryo (fetus, or unborn baby) and become the cells that make up the reproductive system in males and females. These germ cells follow a midline path through the body after development and descend into the pelvis as ovarian cells or into the scrotal sac as testicular cells. Most ovarian tumors and testicular tumors are of germ cell origin. The ovaries and testes are called gonads.
Tumor sites outside the gonad are called extragonadal sites. The tumors also occur along the midline path and can be found in the head, chest, abdomen, pelvis and sacrococcygeal (lower back) area.
Germ cell tumors are diagnosed in about 900 children each year. Germ cell tumors account for 16 percent of all cancers diagnosed in adolescents between the ages of 15 and 19 years old, and nearly 4 percent of cancers diagnosed in children younger than 15 years old.
Germ cell tumors can spread (metastasize) to other parts of the body. The most common sites for metastasis are the lungs, liver, lymph nodes and central nervous system. Rarely, germ cell tumors can spread to the bone, bone marrow and other organs.
What are the different types of germ cells?
Diagnosis of germ cell tumors depends on the types of cells involved. The most common germ cell tumors include the following types:
- Teratomas – contain cells from the three germ layers: ectoderm, mesoderm and endoderm. Teratomas can be malignant or benign, depending on the maturity and other types of cells that may be involved. Teratomas are the most common germ cell tumor found in the ovaries. Sacrococcygeal (tail bone, or distal end of spinal column) teratomas are the most common germ cell tumors found in childhood. Because these sacrococcygeal tumors are often visible from the outside of the body, diagnosis is made early and treatment and/or surgery are initiated early, making the prognosis for this type of germ cell tumor very favorable.
- Germinomas – malignant germ cell tumors. Germinomas also are termed dysgerminoma when located in the ovaries and seminoma when located in the testes. Among children, germinoma, or dysgerminoma, occurs most frequently in the ovary of a prepubescent or adolescent female. Dysgerminoma is the most common malignant ovarian germ cell tumor seen in children and adolescents.
- Endodermal sinus tumor or yolk sac tumors – germ cell tumors that are most often malignant, but also may be benign. These tumors are most commonly found in the ovary, testes and sacrococcygeal areas (tail bone, or distal end of spinal column). When found in the ovaries and testes, they are often very aggressive, malignant and can spread rapidly through the lymphatic system and other organs in the body. Yolk sac tumors are the most common malignant testicular and ovarian tumors in children. Most yolk sac tumors will require surgery and chemotherapy, regardless of stage or presence of metastasis, because of the aggressive nature and recurrence of the disease.
- Choriocarcinoma – a very rare, but often malignant, germ cell tumor that arises from the cells in the chorion layer of the placenta (during pregnancy, a blood-rich structure through which the fetus takes in oxygen, food and other substances while getting rid of waste products). These cells may form a tumor in the placental cells during pregnancy and spread (metastasize) to the infant and mother. When the tumor develops during pregnancy, it is called gestational choriocarcinoma. Gestational choriocarcinoma most often occurs in pregnant females that are 15 to 19 years of age. If a nonpregnant young child develops choriocarcinoma from the chorion cells that originated from the placenta that are still in the body, the term used is nongestational choriocarcinoma.
- Embryonal carcinoma – malignant cells that are usually mixed with other types of germ cell tumors. They occur most often in the testes. These types of cells have the ability to spread to other parts of the body. When these cells are mixed with an otherwise benign type of tumor (mature teratoma), the presence of embryonal carcinoma cells will cause it to become malignant (cancerous).
Many germ cell tumors have multiple types of cells involved. The diagnosis, treatment and prognosis are based on the most malignant of the cells present and the majority type of cells that are present.