Types

Usually, testicular cancer begins in the cells that are responsible for making sperm (known as germ cells). These cells are inside of the testicles, which are a set of glands located inside of the scrotum. There are two main types of testicular germ cell tumors: seminomas and non-seminomas. The most common forms of testicular cancer are found in these two types of cells. 

1. Seminomas

Seminomas grow and spread more slowly than non-seminomas. Some of them produce a protein in the blood called human chorionic gonadotropin (HCG) which can bring on symptoms of testicular cancer. Increased levels of HCG can help the oncologist understand how well treatment is working. 

Over 95% of seminomas can be classified as classical – or typical – seminomas. These occur most often in men between the ages of 25 and 45. Spermatocytic seminomas, a rare variety of seminoma, frequently appear in men who average about 65 years old. These tumors grow slowly and don't spread to other parts of the body as frequently as classical seminomas do. 

2. Non-seminomas

Non-seminomas are typically comprised of multiple types of cancer cells. Interestingly enough, while they can occur outside of the testicles, they only appear in other tissues when cells with the ability to form sperm are found in other parts of the body.

Types of non-seminomas

There are four primary varieties of non-seminomas. They tend to occur most often in men who are between their late teens and early thirties. A majority of tumors are actually a combination of several of these types of cells, but this fact doesn't tend to impact treatment plans. 

The four varieties of non-seminomas are as follows:

• Embryonal carcinomas

  • Found in approximately 40% of testicular tumors

  • Tumors may appear similar to tissues of very early embryos when viewed under a microscope

  • Often grow rapidly

  • Frequently spread outside of the testicle

  • Known to increase blood levels of tumor markers (AFP and HCG) in many cases

• Yolk sac carcinomas

  • The name originates from the fact that their cells resemble a human embryo's yolk sac

  • Also known as endodermal sinus tumors and yolk sac tumors

  • The most common form of testicular cancer in children

  • Pure yolk sac carcinomas are rare in adults

  • Virtually always increase blood levels of the tumor marker AFP

• Choriocarcinomas

  • Rare and fast-growing

  • Likely to spread to other parts of the body

    • Especially the brain, bones, and lungs

  • Usually seen with other types of non-seminoma cells

  • Increases blood levels of the tumor marker HCG

• Teratomas

  • 3 primary varieties

    • Mature-- rarely spread, formed by cells similar to the cells of adult tissues

    • Immature-- cells resemble those of an early embryo, more likely to invade nearby tissues and spread outside the testicle

    • Teratomas with somatic-type malignancy-- very rare, some areas appear similar to mature teratomas, others have areas where the cells have become a type of cancer that usually develops outside of the testicle