Causes of Testicular Cancer

Testicular cancer is an uncommon form of cancer that affects just over 9,000 American men each year. While we have yet to unlock the secrets as to why the disease occurs, scientists believe that a combination of genetic, physiological, and environmental factors play a part. 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. While some of these associations are plausible, others are controversial and unproven.

testicular cancer causes and risk factors
Illustration by Joshua Seong, Verywell 

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).

Broadly speaking, there are two types of germ cell cancer:

  • Seminomas are a type that grows and spreads relatively slowly and primarily affects men between 25 and 45.
  • Non-seminomas typically affect men in their late-teens to early-30s. Non-seminomas are often aggressive and more likely to spread (metastasize).

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 of germ cells 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 strongly in families. In fact, according to scientists with the Institute of Cancer Research in London, the rate of inheritability of testicular cancer is 48.9 percent. That's a striking figure given that genetics usually accounts for less than 20 percent of risk with other forms of cancer.

The risk appears to be greatest if you have a brother with testicular cancer, which raises your risk by more than 800 percent. Having a father with testicular cancer increases your risk four-fold.

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. While genetics plays a large part in many of these factors, there are others related to conditions that occur after birth.

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 50, it does sometimes occur. According to the American Cancer Society, the average age at the time of diagnosis is 33. Only around 6 percent of cases involve young boys or teens, while 8 percent occur in men over 55.

Race and Ethnicity

Race is also a potential risk factor. Statistically speaking, white men have a four-fold greater risk of testicular cancer than either black and Asian men. Hispanic men have only slightly less risk than white men. Native American men, meanwhile, fall somewhere between whites and blacks in this regard.

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 fail to do so by the fourth month, the condition will be diagnosed as cryptorchidism.

While the association is poorly understood, it is believed that the disruption of spermatogenesis (the development of spermatozoa from germ cells) may somehow trigger genetic changes that translate to an increased cancer risk.

From a statistical standpoint, men with cryptorchidism have an eight-fold increased risk of testicular cancer compared to men without. Moreover, men with a partially descended testicle are less likely to develop cancer than men with a testicle that remains in their abdomen.

Strangely, the cancer 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). According to a 2015 study published in the Annals of Oncology, men diagnosed with testicular CIS have no less than a 50 percent risk of developing testicular cancer over the course of five years.

Despite the increased likelihood of a malignancy, there remains considerable controversy as to whether doctors should preemptively treat a CIS to prevent it from turning cancerous. To date, there is still no consensus as to when you should treat a testicular CIS 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 a condition seen in around 20 percent 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 nearly 10-fold.

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 percent 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, was identified as a risk factor back in the 1980s. Recent research suggests that, while the disease can cause micro-calcification in the testicles, the risk of testicular cancer is far less than previously imagined.
  • 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 you are above the average height of 5 feet, 9 inches, your risk of cancer will increase by 13 percent.

    By contrast, early puberty, long presumed to be a risk factor, has been shown to have no effect on a man's personal risk of testicular cancer.

    Lifestyle Risk Factors

    Lifestyle factors don't appear to play as big a role in testicular cancer as they might with other forms of the disease. Still, there are some that contribute.

    Smoking

    While smoking is associated with no less than 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. While it is certainly plausible that cigarettes may contribute, given their carcinogenic effect and impact on sex hormones, research has yet to support the assumption.

    While this shouldn't suggest that smoking is "safe," quitting cigarettes has not been shown to reduce a person's risk of testicular cancer (though it can drastically cut your risk of other health concerns). Furthermore, there is no association between testicular cancer risk and whether you began smoking during adolescence or later in life.

    Marijuana

    Interesting, the same cannot be said for marijuana. In fact, a number of recent studies (including an extensive systematic review of studies conducted by in 2015) have concluded that weekly marijuana use not only increases the risk of testicular cancer by 250 percent but will likely trigger more aggressive forms of the disease.

    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

    Weight is another factor that may or may not contribute to your testicular cancer risk. Some research has actually shown an inverse effect, wherein an increased body mass index (BMI) may lessen the relative risk of the disease.

    A likely explanation of this is the impact of obesity on sex hormones. Consider that height, for example, is largely determined by genetics that trigger higher or lower levels of sex hormones during puberty. By contrast, obesity is associated with decreased male hormone levels, which may have an oddly protective effect. This is supported by evidence that has shown that being overweight neither increases your risk of testicular cancer nor your chance of relapsing after treatment.

    This, again, 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 conceit 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.

    These are not the only factors erroneously linked to testicular cancer. Despite what some people may tell you, you cannot get testicular cancer as a result of:

    • Testicular injury
    • Vasectomy
    • Wearing tight pants
    • Carrying a cell phone in your pocket
    • A urinary tract infection
    • An enlarged prostate

    Interestingly, while prostate cancer also has no association with an increased testicular cancer risk, the opposite does not appear to be true. Current evidence suggests that having had testicular cancer can increase a man's risk of intermediate- to high-risk prostate cancer by no less 500 percent, suggesting a greater need for post-treatment surveillance.

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