Germ cells are unique cells in a developing embryo that become the eggs in the ovaries or the sperm in testicles. Most ovarian tumors and testicular tumors are of germ cell origin. Germ cell tumors are rare and account for 2-4% of all cancers in children and adolescents younger than 20 years, additionally they can metastasize to other body parts. The most common locations 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. Germ cell tumors outside the brain are classified as either gonadal or extragonadal. Gonadal germ cell tumors start and stay in a child’s reproductive organs, the testicles or ovaries. Extragonadal germ cell tumors begin in a child’s reproductive system but travel to different body parts.
What is Germ Cell Tumor?
Germ cells are unique cells in a developing embryo—also called the fetus or unborn baby—that become the eggs in the ovaries or the sperm in testicles. Rarely, during the embryo’s development, these cells may also travel to other areas of the body and form a tumor. These germ cells follow a midline path throughout 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 rare. They account for about 2 to 4 percent of all cancers in children and adolescents younger than 20 1.
Germ cell tumors can metastasize to other body parts. The most common locations 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.
A tumor forms when normal cells change and grow uncontrollably. A tumor can be benign or cancerous. A cancerous tumor is malignant, meaning it can spread to other parts of the body. A benign tumor means the tumor can grow but will not spread.
Types of germ cell tumors
Germ cells may reach the chest, abdomen, or brain. Intracranial germ cell tumors are germ cell tumors that form in the brain. For information on a germ cell tumor in the brain, read about childhood central nervous system tumors additionally, extracranial germ cell tumors are found outside of the brain.
There are two different categories of germ cell tumors that start in the testicles or ovaries: seminomas and nonseminomas. Generally, nonseminomas tend to grow and spread more quickly than seminomas, but prompt diagnosis and treatment are essential for both types of germ cell tumors.
Germ cell tumors outside the brain are classified as either gonadal or extragonadal 2.
- Gonadal germ cell tumours – Gonadal germ cell tumours start and stay in a child’s reproductive organs, which are the testicles or ovaries.
Extragonadal germ cell tumors – Extragonadal germ cell tumors start in a child’s reproductive system but then travel to different parts of the body 3. Germ cells that occur outside the gonads and the brain are called extragonadal and extracranial. These generally happen in early childhood and commonly start in the sacrum and the coccyx, the lowest parts of the spinal column. An extracranial, extragonadal germ cell tumor found in teenagers and young adults is often located in the mediastinum, the centre of the chest.
- 1.Lobo J, Gillis A, Jerónimo C, Henrique R, Looijenga L. Human Germ Cell Tumors are Developmental Cancers: Impact of Epigenetics on Pathobiology and Clinic. IJMS. Published online January 10, 2019:258. doi:10.3390/ijms20020258
- 2.Chung P, Warde P. Testicular cancer: germ cell tumours. BMJ Clin Evid. 2016;2016. https://www.ncbi.nlm.nih.gov/pubmed/26741128
- 3.Rescorla FJ. Pediatric germ cell tumors. Seminars in Pediatric Surgery. Published online February 2012:51-60. doi:10.1053/j.sempedsurg.2011.10.005