Testicle: Definition

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The testicle, also called the testis, is the male reproductive organ that produces sperm and testosterone. Testosterone is the main male sex hormone. A man has two testicles. They sit in the scrotum, and each hangs from the spermatic cord. A pathologist examines testicular tissue, usually after surgeons remove the testicle.

This article explains the parts of the testicle, how sperm leave the body, which conditions affect the testicle, and what the wording on your report means.

What is the testicle?

The testicle is a paired, egg-shaped organ. Each one measures about 5 cm in length in an adult. The testicles lie inside the scrotum, which is the sac of skin below the penis. See penis and scrotum for more about the scrotum. The spermatic cord holds each testicle in place. It contains connective tissue and muscle.

After puberty, the testicles make sperm and testosterone. These two jobs happen in different parts of the organ.

What are the parts of the testicle?

A tough covering surrounds each testicle. Inside, thin walls divide it into small compartments called lobules. The main parts are:

Seminiferous tubules. These are hundreds of tiny tubes. Germ cells line them. Germ cells are the cells that develop into sperm. Doctors call this process spermatogenesis. Sperm then travel through ducts toward the epididymis.
Sertoli cells. These cells sit among the germ cells in the tubules. They support the developing sperm.
Leydig cells. These cells lie in the tissue between the tubules. They make testosterone.
Rete testis. This network collects sperm from the tubules. It passes them on to small ducts that lead to the epididymis.

What is the epididymis?

The epididymis is a coiled tube on top of each testicle. The epididymis stores sperm and lets them mature. During ejaculation, sperm move from the epididymis into the vas deferens. The vas deferens joins the seminal vesicle to form the ejaculatory duct. Sperm then pass through the prostate ducts. They enter the urethra and leave through the tip of the penis.

What conditions affect the testicle?

Most testicular tumors are germ cell tumors. They start from the cells that make sperm. The testicles article lists the main types:

Seminoma. Seminoma is the most common type of testicular cancer in adults. It usually grows slowly and has an excellent outlook.
Embryonal carcinoma. Embryonal carcinoma is a germ cell tumor. It often occurs alongside other germ cell tumor types.
Yolk sac tumor. Yolk sac tumor is the most common testicular tumor in young children. It also occurs in adults as part of a mixed tumor.
Mixed germ cell tumor. A mixed germ cell tumor contains more than one type of germ cell tumor.
Spermatocytic tumor. A spermatocytic tumor is an uncommon germ cell tumor. It usually affects older men and grows very slowly.
Spermatocele. A spermatocele is a common, noncancerous cyst near the testicle. It contains fluid and sperm.

Pathologists also look for germ cell neoplasia in situ (GCNIS). In this early change, the tumor cells stay inside the seminiferous tubules. GCNIS can develop into a germ cell tumor.

How do pathologists examine the testicle?

Pathologists usually examine the whole testicle. Surgeons remove it in an operation called a radical orchiectomy. Doctors rarely take a biopsy of a testicle that may contain a germ cell tumor, because a biopsy could spread the cancer. The pathologist examines the testicle, the epididymis, and the spermatic cord under the microscope. Blood tests for tumor markers often accompany the pathology report. Germ cell tumors often release these proteins into the blood.

What might my report say about the testicle?

Reports describe each part of the specimen separately. Each laboratory phrases it a little differently:

Type of tumor. The report names the germ cell tumor type, or lists each type in a mixed tumor.
Extent of the tumor. The report states whether the tumor stays in the testicle or reaches the epididymis, the spermatic cord, or the scrotum.
Lymphovascular invasion. The report states whether tumor cells entered a lymphatic or blood vessel. See lymphovascular invasion.
GCNIS. The report states whether the pathologist saw germ cell neoplasia in situ in the tissue around the tumor.
Unremarkable. The pathologist saw nothing abnormal in that part of the specimen.

Questions to ask your doctor

What type of tumor does my report describe?
Did the tumor stay inside the testicle?
Did the tumor reach the epididymis, the spermatic cord, or the scrotum?
Did the pathologist see lymphovascular invasion?
Did the pathologist see germ cell neoplasia in situ?
Do I need blood tests for tumor markers?
Do I need imaging or other tests to look for spread?
What follow-up will I need?