Testicular germ cell cancer is a type of cancer that develops in the cells of the testicles responsible for producing sperm. While it’s a rare form of cancer overall, it stands as the most common cancer in young men, particularly those between the ages of 15 and 35. The good news is that when caught early, this cancer is highly treatable, with cure rates exceeding 90% for many patients.

How Common Is Testicular Germ Cell Cancer?

Testicular germ cell cancer represents a relatively uncommon disease in the broader landscape of cancers affecting men. According to available data, it accounts for approximately 1 to 2% of all tumors in males.^[3] Despite these low overall numbers, the disease takes on significant importance when we look at specific age groups. Among men between 15 and 35 years old, testicular cancer becomes the most frequently diagnosed cancer.^[3] In the United States, around 8,000 men were estimated to be diagnosed with this cancer in 2013, with approximately 370 predicted to die from the disease that year.^[3]

More than 90% of testicular cancers begin in the germ cells, which are the cells in the testicles that develop into sperm.^[3] This specific type is known as testicular germ cell cancer. The remaining cases develop from other types of cells in the testicles. Testicular cancer diagnoses are relatively frequent from infancy through early adulthood, with rates increasing and decreasing based on age. Diagnoses occur relatively frequently from infancy up through certain age ranges, though the pattern varies.^[1]

An important observation is that the incidence of testicular germ cell cancer has been continuously rising in many countries, including Europe and the United States.^[3] This increase means that more young men are facing this diagnosis than in previous decades, making awareness and early detection increasingly important.

When we examine which groups are most affected, race and ethnicity play a notable role. Testicular cancer is more common among non-Hispanic white men in the United States and Europe compared to other racial and ethnic groups.^[13] Men who are Caucasian face a risk that is about four to five times greater than that of Black and Asian-American men.^[26]

What Causes Testicular Germ Cell Cancer?

The exact cause of testicular germ cell cancer remains unclear to researchers. What scientists do understand is that the disease develops when cells in the testicles begin to multiply faster than usual, eventually forming a lump or tumor.^[13] The cells that become testicular cancer are usually germ cells, which are the cells responsible for producing sperm in men.^[13]

Testicular germ cell tumors can develop from a condition called germ cell neoplasia in situ, abbreviated as GCNIS. This term describes abnormal cells present in the testicle that look unusual under a microscope but are only found in the small tubes inside the testicle called the seminiferous tubules.^[6] At this stage, these abnormal cells haven’t spread into other parts of the testicle, so GCNIS isn’t considered cancer yet and doesn’t cause any symptoms that a person would notice.

However, GCNIS can progress to become an invasive cancer. Around 50 out of 100 men with GCNIS will develop cancer within five years.^[6] When this happens, the abnormal cells grow beyond the tubules into other parts of the testicles, and the cancer cells can then spread into the lymph nodes and to other parts of the body. It’s important to note that GCNIS doesn’t always progress to become an invasive cancer; some cases remain stable without developing further.

Researchers continue to study why some germ cells transform into cancer cells, but a complete understanding of the biological mechanisms involved is still being developed. What is known is that certain risk factors can increase the likelihood that these cellular changes will occur.

Risk Factors for Testicular Germ Cell Cancer

While the exact cause isn’t fully understood, several factors have been identified that increase a man’s risk of developing testicular germ cell cancer. A risk factor doesn’t guarantee someone will develop the disease, but it does indicate a higher likelihood compared to someone without that factor.

One of the most significant risk factors is having an undescended testicle, also known as cryptorchidism. During fetal development, testicles form in the abdomen and usually descend into the scrotum before birth. When one or both testicles fail to descend, this condition increases the risk of testicular cancer later in life.^[3] Even if surgical correction is performed to move the testicle into the scrotum, the increased risk remains, though surgery before puberty may help lower it somewhat.^[10]

Age is another crucial factor. The disease most commonly affects young and middle-aged men, with about half of testicular cancers occurring in men between the ages of 20 and 34.^[8] The average age at diagnosis is 33 years old.^[13] Teenagers and children account for about 6% of cases, while 8% of cases are diagnosed in men 55 or older.^[13]

Family history also plays a role. Men who have a biological father or brother who had testicular cancer face a greater risk of developing the disease themselves.^[3] Certain inherited genetic conditions, like Klinefelter Syndrome, may also increase risk.^[13] Having testicular cancer in one testicle increases the likelihood of developing a second cancer in the other testicle.^[13]

Other risk factors include having abnormally developed testicles or a personal history of testicular cancer.^[3] Infertility has also been linked to testicular cancer, as some of the same factors that cause male infertility may be related to the development of this disease.^[13] Some research indicates that taller men may have a higher risk, though more study is needed to understand this connection.^[26]

Recognizing the Symptoms

The most common sign of testicular cancer is a painless lump or mass in the testicle.^[5] Many men discover this lump themselves during a self-examination or while bathing. The lump might feel firm or hard to the touch. Because it often doesn’t cause pain, some men may delay seeking medical attention, assuming it’s not serious. However, any new lump in the testicle should be evaluated by a doctor promptly.

Other symptoms can include swelling or a sudden buildup of fluid in the scrotum.^[5] Some men notice a feeling of heaviness in the scrotum, as if something is weighing it down.^[5] A dull ache in the lower belly or groin area may also occur.^[5] While less common, pain or discomfort in a testicle or the scrotum can be present in some cases.^[5]

Some men may notice changes in the size or shape of a testicle, such as enlargement or shrinking. In rare cases, testicular cancer can cause tenderness or enlargement of the breast tissue, a condition called gynecomastia.^[5] Back pain can also occur if the cancer has spread to the lymph nodes in the back of the abdomen.

It’s crucial to understand that these symptoms can be caused by conditions other than cancer. Many non-cancerous conditions affecting the testicles can produce similar symptoms. Additionally, some men with testicular cancer have no symptoms at all, and the cancer is discovered during a routine physical examination or imaging test done for another reason.^[8] Regardless of the cause, any new or unusual symptoms involving the testicles should prompt a visit to a healthcare provider for proper evaluation.

Prevention and Early Detection

Unfortunately, there’s no guaranteed way to prevent testicular germ cell cancer since the exact cause isn’t fully understood. However, awareness and early detection play vital roles in improving outcomes. When testicular cancer is found and treated early, cure rates are extremely high.

Regular self-examination is one of the most important tools for early detection. Many healthcare providers recommend that all men perform a monthly testicular self-exam, especially after puberty and particularly if they have risk factors for the disease.^[26] During a self-exam, men should feel each testicle for any lumps, changes in size or shape, or areas that feel different from normal. The best time to perform this exam is after a warm bath or shower when the scrotal skin is relaxed.

Most healthcare providers agree that a testicular examination should be part of a routine physical exam.^[26] While there’s no standard screening recommendation for testicular cancer like there is for some other cancers, regular check-ups with a doctor can help catch any problems early.^[26] Men should know what their testicles normally feel like, and if they notice any changes, even painless ones, they should get checked quickly.^[23]

For men with an undescended testicle, surgical correction performed before puberty may help lower the risk of testicular cancer, though this benefit isn’t certain.^[10] Men who have had an undescended testicle, even if surgically corrected, should be particularly vigilant about self-examinations and regular medical check-ups since their risk remains elevated.

Education and awareness are crucial, especially for young men who are at the highest risk. Understanding what’s normal for your body and being proactive about seeking medical attention for any changes can make a significant difference in catching cancer early when it’s most treatable.

How Testicular Cancer Affects the Body

To understand how testicular germ cell cancer affects the body, it helps to know what happens when cancer cells form and grow. The testicles contain germ cells that normally develop into mature sperm. When these cells become cancerous, they start multiplying in an uncontrolled way, forming a mass or tumor inside the testicle.

Testicular germ cell tumors are classified into two main groups: seminomas and non-seminomas. Each type accounts for roughly 50% of cases, and they differ in how they grow and respond to treatment.^[12] Seminomas are typically slow-growing cancers that primarily affect men in their 40s or 50s.^[13] Non-seminomas grow more rapidly than seminomas and mainly affect men in their late teens, 20s, and early 30s.^[13]

Non-seminomas include several subtypes: embryonal carcinoma, yolk sac carcinoma, choriocarcinoma, and teratoma.^[13] Each is named after the type of germ cell that makes up the tumor. Some testicular cancer tumors contain a mixture of both seminoma and non-seminoma cells; these mixed tumors are treated as non-seminomas.^[6]

As the tumor grows, it can cause the testicle to enlarge or develop a noticeable lump. The cancer cells may remain confined to the testicle initially, but they have the potential to spread. When testicular cancer spreads, it typically first reaches the lymph nodes in the back of the abdomen, called the retroperitoneal lymph nodes. From there, cancer cells can travel through the lymphatic system or bloodstream to other parts of the body, including the lungs, liver, bones, or brain.

The speed at which testicular cancer grows and spreads depends on the type. Non-seminomas tend to grow larger and spread more quickly than seminomas.^[1] Cancer that has spread to other organs can damage those organs and is more difficult to treat than cancer confined to the testicle.

Testicular cancer cells can also affect the body by producing certain substances called tumor markers. These are proteins that can be detected in the blood. The three main tumor markers for testicular cancer are alpha-fetoprotein (AFP), beta-human chorionic gonadotropin (beta-hCG), and lactate dehydrogenase (LDH).^[10] Seminomas don’t produce AFP, so an elevated AFP level in someone with what appears to be a pure seminoma indicates the presence of non-seminoma cells.^[10] These tumor markers play an important role in diagnosis, treatment planning, and monitoring for recurrence.