Testicular seminoma

Seminoma is a cancer that starts in germ cells, the cells in the testicles that make sperm. Almost all testicular cancers start in germ cells. Doctors sort them into two main types, seminomas and nonseminomas, because the two grow, spread and are treated differently.

Seminomas tend to grow and spread more slowly than nonseminomas. They are very sensitive to radiation, and chemotherapy works well against them too. Only a tumor made entirely of seminoma cells counts as a seminoma. A tumor that has both seminoma and nonseminoma cells is treated as a nonseminoma. So is a tumor that looks like seminoma but raises a blood marker called AFP (alpha-fetoprotein), because seminomas do not make AFP.

Testicular cancer is the most common cancer in men aged 20 to 39, with the highest rates between 25 and 34. In the United States, seminoma is the most common type of testicular germ cell tumor. It is most often found in men aged 25 to 45.

Doctors do not know exactly what causes seminoma. In the earliest stage, abnormal cells are found in the tiny tubes of the testicle where sperm begin to form. These cells are called germ cell neoplasia in situ. They are not yet invasive cancer, but they may become cancer and spread into nearby tissue.

Some things raise the risk. One is a testicle that did not move down into the scrotum before birth (an undescended testicle, or cryptorchidism). Others are a testicle that did not develop normally and a past testicular cancer. A father or brother who had testicular cancer also raises the risk. So do Klinefelter syndrome and HIV infection. In U.S. cancer registry data for 2021, these cancers were most common in Hispanic and non-Hispanic White men, and least common in Black men.

Having a risk factor does not mean a man will get testicular cancer, and it also develops in men with no known risk factor. There is no link between a vasectomy and testicular cancer.

Some men have no symptoms at first. Signs can include a painless lump or swelling in a testicle, or a change in how the testicle feels. Some men have a dull ache in the lower belly or groin. Others have a sudden build-up of fluid in the scrotum, or pain in the testicle or scrotum. Other conditions can cause these signs too.

Seminoma can spread through the lymph system to lymph nodes at the back of the belly (the retroperitoneum). From there it can reach lymph nodes farther away or the lungs. About 1 in 10 seminomas that have spread reach other organs, such as the liver, bone or brain. That is the main sign of a harder course.

Blood tumor markers help doctors follow the cancer. Seminomas do not make AFP. But some raise another marker, beta-hCG. Before surgery it is raised in about 1 in 7 men whose seminoma is only in the testicle, and in about half of men whose seminoma has spread.

After surgery, the choice between surveillance and more treatment can feel hard, because several options lead to similar cure rates. Surveillance means scans and blood tests on a set schedule. A typical plan is every 4 months for the first 3 years, every 6 months for the next 3 years, then once a year for 4 more years. Relapses after 5 years are unusual, but they can happen in as many as 4% of men.

Many men already have low or abnormal sperm counts before treatment. Chemotherapy, radiation and lymph node surgery can each affect fertility, so care teams usually offer sperm banking (freezing sperm) before any treatment beyond removing the testicle. Most men can still father children afterward. In two large studies, about 70% did. Doctors usually advise waiting at least 3 months after chemotherapy before conceiving, unless using sperm frozen before treatment.

Because most men are cured and live for decades, long-term health gets close attention. Cisplatin can cause hearing loss at high pitches, usually outside the range of everyday speech. Some survivors have nerve damage that causes numbness or tingling (peripheral neuropathy). Chemotherapy and radiation raise the long-term risk of heart disease, and chemotherapy is linked to metabolic syndrome and low testosterone. Both can raise the risk of a second cancer years later. About 2% of men develop cancer in the other testicle within 15 years, so checkups include it.

High-dose chemotherapy with stem cell rescue is much harder on the body than standard treatment. The strong chemotherapy also destroys blood-forming cells, so blood counts drop very low until the returned cells take hold. That raises the risk of infection and bleeding for a time. Many centers give two rounds of high-dose chemotherapy, each followed by the man’s own cells (a tandem transplant). In CIBMTR registry data, 77% of these transplants for male germ cell tumors in 2010–2015 were tandem. In a 2025 review that pooled studies from several decades, 7.5% of people died from high-dose treatment itself, compared with 3% after standard-dose salvage chemotherapy. The review notes that better supportive care has lowered this risk over time.

No donor is needed for seminoma. Surgery, surveillance, radiation and chemotherapy use no one else’s cells. When high-dose chemotherapy with stem cell rescue is used, the stem cells are the man’s own, collected and frozen before treatment. No family member needs to be tested as a match.

Donor (allogeneic) transplants are not part of care for testicular germ cell cancer. In EBMT’s 2025 recommendations, donor transplants for germ cell tumors are marked not applicable in adults and generally not recommended in children and teens.

So joining a registry is not a step that helps a man with seminoma. Registries serve patients with leukemia, lymphoma and other blood disorders, where an unrelated volunteer may be the only possible donor.