Types of Testicular Cancer

Most testicular cancer begins in germ cells, specialized cells that make sperm. The two most common types of testicular germ cell tumors are seminomas and nonseminomas. 

1. Seminomas

Seminomas tend to grow slowly and are usually easy to treat since they are less likely to metastasize. Some of them produce a protein in the blood called human chorionic gonadotropin (HCG) which contributes to 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 are more aggressive than seminomas and are more likely to spread past the testicle. There are four main subtypes of nonseminoma tumors that include embryonal carcinoma, yolk sac carcinoma, choriocarcinoma, and teratoma. Typically, these types of tumors occur in men between their late teens and early 30s. 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
  • Tend to grow rapidly
  • Often spread outside of the testicle
  • Tumors sometimes appear similar to tissues of very early embryos when viewed under a microscope
  • Known to increase blood levels of tumor markers (AFP and HCG) in many cases

Yolk sac carcinoma

  • Their cells resemble a human embryo’s yolk sac, hence the name
  • Also referred to as endodermal sinus tumors and yolk sac tumors
  • Pure yolk sac carcinomas are rare in adults
  • The most common form of testicular cancer in children
  • 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
  • Most often 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