Causes of Testicular Cancer

While we have yet to unlock the secrets of why testicular cancer occurs, scientists believe that a combination of genetic, physiological, and environmental factors is involved. In recent years, no less than 19 chromosomal mutations have been linked to testicular cancers. Younger age, race, an undescended testicle, and testicular development problems are also commonly associated with the disease.

Other risk factors—including horseback riding, competition cycling, smoking, weight, and vasectomy—have long been presumed to either cause or contribute to testicular cancer but are not proven to have any association with the condition.

This article explores the causes and risk factors for testicular cancer.

Genetics

There are several different types of testicular cancer. The vast majority are classified as germ cell cancers. These are malignancies that arise from the cells that produce spermatozoa (immature sperm).

Germ cell cancers have specific genetic alterations. Under normal circumstances, the cells of our body have two sets of 23 chromosomes—one set from each biological parent. Some cells in germ cell cancers may have three sets of chromosomes (triploid) and even four (tetraploid).

A characteristic genetic alteration that almost all germ cell cancers share is an extra copy of a fragment of chromosome 12 (isochromosome 12p), a chromosomal anomaly associated with both testicular and ovarian cancers.

More than with other types of cancer, these mutations run in families. In fact, according to scientists from the Institute of Cancer Research in London, the rate of inheritability of testicular cancer is 48.9%. That's a striking figure given that genetics usually accounts for less than 20% of the risk with other forms of cancer.

Common Factors

By and large, the most common risk factors for testicular cancer are non-modifiable, meaning that you are either born with them or cannot change them. Some risk factors are related to lifestyle.

Age

Age plays a major role in testicular cancer risk insofar as the disease mostly affects men between the ages of 15 and 35. While the disease is rare before puberty or after age 50, it does sometimes occur at those ages.

Race and Ethnicity

Statistically, White men have a four-fold greater risk of testicular cancer than either Black or Asian men. Hispanic men have only slightly less risk than White men. Native American men, meanwhile, have a risk between Whites and Blacks.

Globally, the risk of testicular cancer is highest among men in the United States and Europe and lowest among men living in Asia and Africa.

Undescended Testicle (Cryptorchidism)

One of the established risk factors for testicular cancer is an undescended testicle. In the course of normal male development, the testicles will typically descend down the inguinal canal into the scrotum by the time you are born. If they don't do so by four months of age, the condition will be diagnosed as cryptorchidism.

Men who have had cryptorchidism have an eight-fold increased risk of testicular cancer. Moreover, men with a partially descended testicle are less likely to develop cancer than men with a testicle that remains in their abdomen.

Testicular cancer or atrophy (which can be associated with lower testosterone production or lower fertility) will usually, but not always, affect the undescended testicle.

Carcinoma in Situ

Carcinoma in situ (CIS) is an abnormal growth of tissue often referred to as precancer, although not all cases of CIS will become malignant.

Despite the increased likelihood of malignancy, there remains considerable controversy as to whether doctors should preemptively treat CIS to prevent it from turning cancerous. To date, there is no consensus as to when testicular CIS should be treated or what level of radiation treatment is appropriate.

As such, most doctors will take a watch-and-wait approach rather than expose a man to potentially unnecessary radiation or surgery.

Testicular Microlithiasis

Calcium deposits in the testicles, known as testicular microlithiasis, is seen in around 20% of men who have difficulty conceiving. While microlithiasis on its own is not associated with testicular cancer, in men with testicular CIS, the risk of developing a malignancy will increase.

Other Possible Causes

There are other conditions that may increase your risk of testicular cancer. Some of these are strongly supported by research, while others confer​ a relatively small increase in risk.

Among them:

• A prior history of testicular cancer is associated with recurrence in around 10% of men, and this is usually the result of either undertreatment or the lack of routine post-treatment monitoring.
• HIV may increase your risk of testicular cancer due to the persistent inflammation associated with the infection. However, the evidence to date has been mixed, with some studies suggesting a 10-fold increased risk and others showing no association at all.
• Klinefelter syndrome, a genetic disorder in which a man has an extra X chromosome, can cause micro-calcification in the testicles and increase the risk of testicular cancer.
• Tall height has been implicated as a risk factor, likely due to the increased production of sex hormones during puberty. While the research to date has been limited, a 2014 study from Yale University concluded that for every two inches above the average height of 5 feet, 9 inches, your risk of cancer will increase by 13%.

Lifestyle Risk Factors

Lifestyle factors can have a minimal effect on testicular cancer risk, but they haven't been found to play a significant role.

Smoking

While smoking is associated with at least 16 types of cancer—including those affecting the lungs, mouth, throat, bladder, kidneys, pancreas, stomach, liver, bowel, cervix, and ovaries—its role in testicular cancer is far less clear.

This shouldn't suggest that smoking is "safe" —quitting cigarettes can drastically cut your risk of other health problems besides testicular cancer.

Marijuana

Marijuana may be a risk factor for testicular cancer.

According to the research, exposure to delta-9-tetrahydrocannabinol (THC), the psychoactive chemical in cannabis, can disrupt spermatogenesis in the same way that an undescended testicle can.

Obesity

Being overweight neither increases your risk of testicular cancer nor your chance of relapsing after treatment.

This shouldn't suggest that putting on a few extra pounds is a good thing. In fact, if you are overweight and undergo testicular cancer treatment, your risk of cardiovascular risk may skyrocket. This is because testicular cancer treatment will often result in hypogonadism (low testosterone production), a condition closely associated with metabolic syndrome.

Myths and Misconceptions

When former Tour de France cyclist Lance Armstong was diagnosed with testicular cancer in 1996, it was largely presumed that years of riding on a bicycle saddle was to blame. It is a misperception that persists to this day, suggesting that repetitive actions such as cycling, horseback riding, or motorcycling are major contributors, if not the primary cause, of testicular cancer.

This is untrue. Years of research has yet to reveal any link between these or any other strenuous physical activities and the risk of testicular cancer.

Current evidence suggests that having had testicular cancer can increase a man's risk of intermediate- to high-risk prostate cancer at least fivefold, suggesting a greater need for post-treatment surveillance.

However, prostate cancer does not increase testicular cancer risk.