Testicular cancer develops in the testicles (testes), the male
reproductive glands. The testicles are located in the scrotum (membranous
pouch below the penis) and are suspended from the body by the spermatic
cord. They produce sperm (male reproductive cells) and testosterone.
Testicular cancer is treated successfully in more than 95% of cases.
The testicles are primarily made up of a mass of seminiferous tubules in
which sperm develop. The tubules are lined with Sertoli cells, which protect
and supply nutrients to developing sperm. Sertoli cells also secrete the
hormone inhibin, which is involved in the regulation of sperm production.
Leydig cells, located in tissue between the seminiferous tubules, secrete
testosterone and androsterone. These hormones stimulate the development of
male sex organs, beard growth, muscle mass, and deepening of the voice.
Most (95%) testicular cancer originates in undeveloped cells (germ cells)
that produce sperm. These tumors, called germ cell tumors (GCTs), are most
common in men between the ages of 20 and 40 and are curable in more than 95%
of cases. There are two main types: seminomas and nonseminomas. A third
type, called stromal tumors, develops in the supporting tissues of the
Approximately 40% of GCTs are seminomas, which are classified as either
typical or spermatocytic. Typical seminomas account for 90% of this type.
They often cause unilateral (on one side) testicle enlargement or more often
a painless lump in the testicle. Spermatocytic seminomas grow slowly,
usually do not spread to other parts of the body (metastasize), and are most
common around age 65.
Nonseminomas account for 60% of GCTs and develop in younger men (usually
between 15 and 35). Most nonseminomas contain cells from at least two
subtypes, including the following:
- Choriocarcinoma (rare; aggressive; likely to metastasize)
- Embryonal carcinoma (accounts for 20% of cases; likely to metastasize)
- Teratoma (usually benign in children; rarely metastasize)
- Yolk sac carcinoma (most common in young boys; rare in men)
Testicular cancer may also develop in the supportive, hormone-producing
tissue of the testicles (stroma). This type accounts for 4% of testicular
cancer in men and 20% in boys. Types of stromal tumors include Leydig cell
tumors and Sertoli cell tumors.
Seventy-five percent of Leydig cell tumors develop in men and 25%
develop in boys. Most tumors of this type are benign and are treated
successfully with surgery. If the tumor metastasizes, it often does not
respond well to radiation or chemotherapy and the prognosis is poor.
Sertoli cell tumors develop in Sertoli cells that nourish the
sperm-producing germ cells. These tumors are usually benign; metastatic
tumors of this type are rare, yet resistant to treatment.
Secondary tumors in the testicles usually migrate from the lymph
or lymph nodes. Testicular lymphoma is more common than primary testicular
cancer in men over 50. Other cancers (e.g., prostate, lung, skin) may also
spread to the testicles.