What is testicular cancer?
Testicular cancer can start in one or both testicles. It is most often found in young men but can occur at any age. This type of cancer can be treated successfully and very often cured.
The testicles (or testes) are part of the male reproductive system. In adult men, each one is normally a little smaller than a golf ball. They are held in a sac of skin called the scrotum. The scrotum hangs beneath the base of the penis.
The testicles have 2 main functions:
- They make the male hormones such as testosterone.
- They make sperm, the male cells that combine with a female egg cell to start a pregnancy.
Once they’re made in the testicles, the sperm cells are stored in the epididymis, a small coiled tube behind each testicle, where they mature.
During ejaculation, the sperm cells are carried from the epididymis through small tubes (the vas deferens) to the seminal vesicles. Here they mix with fluid from the vesicles and from the prostate and other glands to form semen. This fluid travels through a tube (the urethra) in the center of the penis and out of the body. See the picture below.
Testicles are made of several kinds of cells, each of which can develop into one or more types of cancer. It is important to know which kind of cell the cancer started from because each type of cancer is treated differently. They also differ in the chance of survival for the patient (prognosis).
Main types of testicular tumors
Germ cell tumors
More than 9 out of 10 of cancers of the testicles start in the germ cells. As used here, the term “germ” means seed. Germ cell tumors start in the cells that make sperm.
There are 2 main types of germ cell tumors in men, which occur about equally:
Seminomas: These tumors tend to grow and spread more slowly than most other testicular cancers. There are different types of seminomas. They usually develop in men between 25 and 45.
Non-seminomas: These tumors tend to develop earlier in life than seminomas. They are often found in men between their late teens and early 30s. There are 4 main types of non-seminomas:
- Embryonal carcinoma
- Yolk sac carcinoma
Most tumors are a mix of 2 or more of these different types. But all non-seminoma cancers are treated the same way.
Mixed germ cell tumors: These cancers have both seminoma and non-seminoma cells. They are treated as non-seminomas because they grow and spread like non-seminomas.
Carcinoma in situ: Testicular germ cell cancers may begin as a non-invasive form of the disease called carcinoma in situ (CIS). The cells don’t look normal under the microscope, but they have not yet spread beyond the seminiferous tubules (where sperm cells are formed). Carcinoma in situ may not always go on to become invasive cancer.
Experts don’t agree about the best treatment for CIS. Since CIS doesn’t always become an invasive cancer, many doctors feel that observation (watching and waiting) is the best course of action.
These tumors start in the cells that make hormones and in the supportive tissues (the stroma) of the testicles. They make up less than 1 in 20 adult testicular tumors but up to 1 in 5 testicular tumors in boys. The 2 main types of stromal tumors are:
- Leydig cell tumors
- Sertoli cell tumors
Stromal cell tumors are often benign (not cancer). They usually do not spread beyond the testicle and can be cured by surgery. But a few stromal cell tumors spread to other parts of the body (metastasize). Tumors that have spread tend to have a poor outlook because they do not respond well to chemotherapy or radiation treatment.
Secondary testicular tumors
Tumors start in another organ and then spread to the testicle are called secondary testicular tumors. These are not true testicular cancers – they are named and treated based on where they started.
Lymphoma is the most common cancer that does this. In boys with acute leukemia, the leukemia cells can sometimes form a tumor in the testicle.
Cancers of the prostate, lung, skin, kidney, and other organs can also spread to the testicles. The outlook for these cancers tends to be poor because very often these cancers have spread widely to other organs, too. Treatment depends on the type of cancer.
Last Medical Review: 01/02/2014
Last Revised: 01/09/2015