Though it’s a rare condition, testicular cancer is still a threat to men, particularly those aged 15 to 34. About 8,400 men in the United States are diagnosed with testicular cancer every year. A good way to understand the disease better is to know more about the different types of testicular cancer, of which there are many.

Types of Testicular Cancer: Germ Cell Tumors

Most testicular cancers start in the germ cells, the cells that produce sperm inside the testicles. In fact, more than 90 percent of testicular cancers grow here. These germ cell tumors are further subdivided into two main categories: seminomas and nonseminomas.

Types of Testicular Cancer: Seminomas

The most common type of testicular cancer, seminomas, occurs most frequently in men between their late 30s and early 50s. Though there are subtle medical differences between a seminoma and a non-seminoma, and you can see the difference under a microscope, the key thing you need to know about seminomas is that they are slower-growing than non-seminomas. That doesn’t necessarily mean that receiving a seminoma diagnosis is good news, but it does mean there is less of a chance that it will spread to other parts of the body.

Also, seminomas are easier to treat than non-seminomas. “Seminomas are highly sensitive to radiation,” says Otis W. Brawley, MD, chief medical officer of the American Cancer Society. “So if a man [has] a seminoma, we can often cure him with surgery and very low doses of radiation.”

Types of Testicular Cancer: Non-seminomas

Other germ cell tumors are classified as “non-seminomas.” There are four types of non-seminomas:

  • Embryonal carcinoma
  • Yolk sac carcinomas
  • Choriocarcinomas
  • Teratomas

There are subtle differences between each type of non-seminoma, but the chief characteristics of the group are that they grow more quickly than seminomas, and they are more difficult to treat. They typically occur in men between their late teens and early 40s.

A doctor can tell which type of non-seminoma you have with a blood test, which will indicate elevations of certain protein “markers” in the bloodstream. Then they treat it accordingly.

“While seminomas react well to radiation, most non-seminomas do not,” says Bradley C. Leibovich, MD, an associate professor of urology at the Mayo Clinic in Rochester, Minn. “Each non-seminoma responds a little differently to treatment. Yolk sac carcinomas, for example, respond well to chemotherapy, but teratomas generally don’t.”

One of the rarest and most aggressive types of nonseminoma, says Dr. Leibovich, is choriocarcinomas. “These tend to spread quickly through the bloodstream to other parts of the body,” he says. That’s why early detection is critical.

Types of Testicular Cancer: Stromal Tumors

Rarer forms of cancer can develop in the testicle tissues that produce hormones or serve other supportive functions. These tissues are known as stroma, so the cancers are classified as stromal tumors.

One part of the stroma is made up of Leydig cells that produce male hormones, such as androgen and testosterone. In rare instances, tumors can develop in these cells. With Leydig cell tumors, early detection is key. The prognosis is good if the tumors stay within the testis, but it becomes difficult to cure if they spread outside it. The good news is that Leydig cell tumors usually remain in the testis.

The other type of stromal tumors can develop in the Sertoli cells, which feed the germ cells and help them do their job. Their diagnosis and treatment are quite similar to that of Leydig cell tumors.

Types of Testicular Cancer: Cancer That Spreads to the Testicles

Though not specifically testicular cancers, other forms of cancer can spread, or metastasize, to the testicles. The most common of these is lymphoma, but leukemia and cancers of the prostate, lung, skin, kidney, and, in rare instances, other organs can also spread to the testicles.

Although there are a number of different types of testicular cancer, they are rarely fatal if caught and treated early. Monthly self-exams are the best way to detect testicular cancer early. If you notice any unusual symptoms, such as a lump in your testicle or discomfort in your groin or stomach, see your doctor immediately.