Key Points for This Section

Testicular cancer is a disease in which malignant (cancer) cells form in the tissues of one or both testicles. Testicular cancer is the most common cancer in men aged 15 to 35 years. A condition called cryptorchidism (an undescended testicle) is a main risk factor for developing testicular cancer.

Testicular cancer is a disease in which malignant (cancer) cells form in the tissues of one or both testicles.

The testicles are 2 egg-shaped glands located inside the scrotum (a sac of loose skin that lies directly below the penis). The testicles are held within the scrotum by the spermatic cord, which also contains the vas deferens and vessels and nerves of the testicles.

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Anatomy of the male reproductive and urinary systems, showing the testicles, prostate, bladder, and other organs.

The testicles are the male sex glands and produce testosterone and sperm. Germ cells within the testicles produce immature sperm that travel through a network of tubules (tiny tubes) and larger tubes into the epididymis (a long coiled tube next to the testicles) where the sperm mature and are stored.

Almost all testicular cancers start in the germ cells. The two main types of testicular germ cell tumors are seminomas and nonseminomas.

Testicular cancer is the most common cancer in men aged 15 to 35 years.

Testicular cancer is very rare, but it is the most common cancer found in men between the ages of 15 and 35.

Although there has been an increase in the number of new cases in the last 40 years, the number of deaths caused by testicular cancer has decreased greatly because of better treatments for it.

A condition called cryptorchidism (an undescended testicle) is a main risk factor for developing testicular cancer.

Anything that increases the chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. People who think they may be at risk should discuss this with their doctor. Risk factors for testicular cancer include the following:

• Having cryptorchidism (an undescended testicle).
• Having testicles that form in an unusual way.
• Being white.
• Having a personal or family history of testicular cancer.
• Having Klinefelter syndrome.
• Having testicular carcinoma in situ.

Glossary Terms

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.

A group of abnormal cells that remain in the tissue in which they first formed. These abnormal cells may become cancer and spread into nearby normal tissue.

A condition in which one or both testicles fail to move from the abdomen, where they develop before birth, into the scrotum. Cryptorchidism may increase the risk for development of testicular cancer. Also called undescended testicles.

A record of a person's current and past illnesses, and those of his or her parents, brothers, sisters, children, and other family members. A family history shows the pattern of certain diseases in a family, and helps to determine risk factors for those and other diseases.

A reproductive cell of the body. Germ cells are egg cells in females and sperm cells in males.

A type of tumor that begins in the cells that give rise to sperm or eggs. Germ cell tumors can occur almost anywhere in the body and can be either benign or malignant.

An organ that makes one or more substances, such as hormones, digestive juices, sweat, tears, saliva, or milk. Endocrine glands release the substances directly into the bloodstream. Exocrine glands release the substances into a duct or opening to the inside or outside of the body.

A genetic disorder in males caused by having one or more extra X chromosomes. Males with this disorder may have larger than normal breasts, a lack of facial and body hair, a rounded body type, and small testicles. They may learn to speak much later than other children and may have difficulty learning to read and write. Klinefelter syndrome increases the risk of developing extragonadal germ cell tumors and breast cancer.

A bundle of fibers that receives and sends messages between the body and the brain. The messages are sent by chemical and electrical changes in the cells that make up the nerves.

A group of testicular cancers that begin in the germ cells (cells that give rise to sperm). Nonseminomas are identified by the type of cell in which they begin and include embryonal carcinoma, teratoma, choriocarcinoma, and yolk sac carcinoma.

An external male reproductive organ. It contains a tube called the urethra, which carries semen and urine to the outside of the body.

Something that may increase the chance of developing a disease. Some examples of risk factors for cancer include age, a family history of certain cancers, use of tobacco products, certain eating habits, obesity, lack of exercise, exposure to radiation or other cancer-causing agents, and certain genetic changes.

In males, the external sac that contains the testicles.

A type of cancer of the testicles. Seminomas may spread to the lung, bone, liver, or brain.

The male reproductive cell, formed in the testicle. A sperm unites with an egg to form an embryo.

One of two egg-shaped glands inside the scrotum that produce sperm and male hormones. Also called testis.

Cancer that forms in tissues of the testis (one of two egg-shaped glands inside the scrotum that make sperm and male hormones). Testicular cancer usually occurs in young or middle-aged men. Two main types of testicular cancer are seminomas (cancers that grow slowly and are sensitive to radiation therapy) and nonseminomas (different cell types that grow more quickly than seminomas).

A hormone made mainly in the testes (part of the male reproductive system). It is needed to develop and maintain male sex characteristics, such as facial hair, deep voice, and muscle growth. Testosterone may also be made in the laboratory and is used to treat certain medical conditions.

A coiled tube that carries the sperm out of the testes.