Types of testicular cancer

Determining which treatments to use for testicular cancer may depend on the kind of cells involved. Many types of cells are found in the testicles, all of which may become cancerous. However, two main types of tumors account for most testicular cancers: germ cell tumors and non-germinal tumors.

Nearly all testicular cancers are germ cell tumors, meaning that they start in a particular type of cell called a germ cell.

Germ cells produce sperm. Germ cell tumors make up about 95 percent of testicular cancer cases, according to the National Cancer Institute. The other 5 percent of cases are non-germinal tumors, which include rare types such as Leydig cell tumors and Sertoli cell tumors.

Germ cell tumors

Within germ cell tumors are three types of testicular cancers:

• Seminomas may be slightly more common, accounting for about 55 percent of all testicular germ cell tumors in the United States, according to a 2014 study in Andrology.
• Non-seminomas account for about 44 percent of testicular germ cell tumors, according to the same study.
• The remaining 1 percent are spermatocytic seminomas, according to a 2011 study in BMC Research Notes. These are extremely rare, generally not aggressive, and affect older men.

Many testicular cancers are mixed germ cell tumors, meaning that they have both seminoma and non-seminoma cells. Only tumors that have 100 percent seminoma cells are considered seminomas, while non-seminomas contain different types of cells.

Blood tests are one of the ways to determine the type of testicular tumor. Different types of tumors produce high levels of specific proteins, and testing the blood for those proteins indicates which type of tumor is present. Non-seminomas usually produce high levels of proteins such as alpha-fetoprotein (AFP). Seminomas never cause an increase in AFP levels, so if there’s too much AFP in the blood, this is a good indication that the tumor is a non-seminoma type.

Risk factors for testicular cancers include:

• Older age
• Undescended testicle at birth
• Close relatives with testicular cancer

Seminoma: Of the two subtypes, classical (typical) seminomas are more likely to occur in men age 30 to 50. Spermatocytic seminomas are less common and found more frequently in men age 55 and older. However, both types of seminoma tumors may occur in all age groups.

Almost all seminomas are the classical type (more than 95 percent).

Spermatocytic seminomas are extremely rare, accounting for less than 1 percent of all testicular cancers. These cancers are slow-growing and rarely spread (metastasize) to other parts of the body.

Having human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) may also increase the risk of developing a seminoma.

Non-seminoma: These tumors have four main subtypes, including embryonal carcinoma, yolk sac carcinoma, choriocarcinoma and teratoma. These tumors generally occur between the teenage years and early 30s. They also tend to grow and spread more quickly than seminomas. Testicular cancer may involve one or both kinds of tumors.

Non-seminoma tumors usually contain a mix of two or more different cells. They may be teratoma cells, yolk sac cells, choriocarcinoma cells, embryonal carcinoma cells or even seminoma cells. No matter what mix of cells the tumor contains, treatment is usually similar for all non-seminoma testicular cancers.

• Embryonal carcinoma cells occur in about 40 percent of all testicular tumors, according to the American Cancer Society (ACS). Doctors determine whether a tumor contains these cells (which look like very premature cells that are present in an embryo) by studying it under a microscope. Non-seminoma tumors with this type of cell are often fast-growing and spread easily.
• Yolk sac carcinoma cells resemble those that make up the yolk sac of an embryo, which helps transfer nutrients to the embryo before the placenta forms. Children who develop testicular cancer typically have yolk sac carcinoma. In children, treatment is usually successful, but yolk sac carcinoma in adults may be more difficult to treat.
• Choriocarcinoma cells are usually mixed in with other cell types in non-seminoma tumors. Choriocarcinoma cells on their own form a very rare and aggressive type of testicular tumor. Mixed tumors are usually more treatable than pure choriocarcinomas.
• Teratoma cells have three layers that resemble the three layers of an embryo. These cells are usually mixed in with other types of cells in non-seminoma tumors and rarely form pure teratomas. 

Rare testicular tumors

Stromal tumors are sometimes referred to as gonadal stromal tumors. They are a rare form of testicular cancer, accounting for about 5 percent of cases in adults. However, they account for up to 20 percent of testicular cancer cases in children, according to the ACS.

In addition to producing sperm for reproduction, the testicles, or male gonads, are also part of the endocrine system, a series of hormone-producing glands. The stromal cells in the testes produce male sex hormones (androgens) such as testosterone.

Most stromal tumors are benign (not cancerous), meaning the tumor cells typically don’t spread (metastasize) to other parts of the body. However, stromal tumors that do spread sometimes don’t respond to conventional treatments, like chemotherapy or radiation. Stromal tumors include Leydig cell tumors and Sertoli cell tumors.

• Leydig cell tumors start in testicle cells that are typically responsible for producing male hormones (androgens). Leydig cell tumors are usually benign. However, a subset of these tumors is cancerous and may spread beyond the testicles. Benign Leydig cell tumors are typically removed and treated with surgery, but cancerous Leydig cell tumors may be difficult to treat. Sertoli cell tumors start in cells called
• Sertoli cells, which help germ cells produce sperm. Most of the time, these tumors are benign. But like Leydig cell tumors, they may be tough to treat if they spread and become cancerous.

Lymphoma

Lymphoma is a cancer that typically starts in white blood cells, which are part of your immune system. However, on rare occasions, lymphoma starts in the testicles. According to a 2014 review in the journal Blood, the rate of yearly cases of primary testicular lymphoma (PTL) is estimated to be around 0.09 to 0.26 per every 100,000 people. It most often affects older men older than 60.

Carcinoma in situ of the testicle

Carcinoma in situ (CIS) of the testicle is an early form of testicular cancer that may or may not progress into invasive cancer and cause problems. CIS cells don’t look like normal, healthy cells, but they also aren’t spreading yet.

CIS usually doesn’t cause noticeable symptoms, and a biopsy is the only way to discover it. CIS may not require immediate treatment, as not all cases become invasive. If CIS does start to spread, it grows farther into the testicle, where it may reach other parts of the body through the lymph system or the blood.

Recurrent testicular cancer

After treatment for testicular cancer concludes and you’re considered to be in remission (no evidence of cancer), there’s a chance that the cancer may return. Patients in remission need regular checkups to make sure their cancer hasn’t returned. Recurrent testicular cancer may occur in the testicles, near the testicles or in a completely different part of the body. Usually, recurrent testicular cancer doesn’t affect the testicle, as the testicle is often removed during the initial treatment.