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Types of Testicular Cancer

Testicular cancer most often begins in germ cells (cells that make sperm) that are inside the testicles. There are two main types of testicular germ cell tumors: seminomas and nonseminomas. The most common forms of testicular cancer are found in these two types of cells.

1. Seminomas

Seminomas grow and spread more slowly than nonseminomas. 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.

Most (over 95%) seminomas are classified as classic (typical) seminomas. These occur most often in men between the ages of 25 and 45. Spermatocytic seminomas, which are rare, tend to occur in older men who average about 65 years old. These tumors grow slowly and don't spread to other parts of the body as frequently as classic seminomas do.

2. Nonseminomas

Nonseminoma tumors have four main subtypes: embryonal carcinoma, yolk sac carcinoma, choriocarcinoma, and teratoma. These types of tumors usually occur in men between their late teens and early 30s. They also tend to grow and spread more quickly than seminomas. 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.

Embryonal carcinoma

  • 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 carcinoma

  • 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

Choriocarcinoma

  • 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

Teratoma

  • 3 primary varieties
    • Mature: formed by cells similar to the cells of adult tissues and rarely spread
    • 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