Testicular cancer, while relatively uncommon, is a significant concern, particularly among younger men, primarily affecting individuals between 15 and 45. While its exact origins are not fully clear, researchers have identified several factors that increase the likelihood of developing the disease. This article clarifies the current understanding of its causes and associated risk factors.
Identified Risk Factors
One of the most recognized risk factors for testicular cancer is having an undescended testicle, a condition known as cryptorchidism. During fetal development, testicles typically form in the abdomen and descend into the scrotum before birth. If one or both testicles do not descend properly, the risk of developing testicular cancer increases significantly, even if surgery is performed later to correct the position. This elevated risk might be due to the abnormal cellular environment or higher temperature within the abdomen compared to the scrotum.
A personal history of testicular cancer in one testicle also increases the risk of developing it in the other. Approximately 3% to 4% of men who have had cancer in one testicle will eventually develop it in the remaining testicle.
Family history plays a role as well, with an increased risk for individuals who have a father or brother diagnosed with testicular cancer. While most cases do not involve a family history, a brother with the disease can increase risk by eight to twelvefold, and a father by two to fourfold. This suggests a genetic component, although the disease is not always directly inherited.
Testicular cancer is more common in white men, particularly those in North America and Europe, compared to men of other racial or ethnic backgrounds. The reasons for this disparity are not fully understood. Additionally, age is a factor, with the majority of diagnoses occurring in men between 15 and 35, though it can occur at any age. The average age of diagnosis is around 33 years.
Some studies have explored a potential link between body size and testicular cancer. For instance, a higher birth weight and taller adult stature have been associated with an increased risk in some research. However, findings regarding adult body mass index (BMI) have been inconsistent, with some studies showing no clear association or even an inverse relationship. These body size associations are generally considered less clear or strong than other established risk factors.
Genetic and Inherited Influences
Genetic factors contribute significantly to testicular cancer susceptibility, with nearly half of the risk attributed to inherited DNA. While a specific single gene with a large effect has not been identified, the risk is thought to stem from a combination of many minor variations in DNA. This indicates a complex genetic predisposition rather than a direct inheritance pattern.
Research has identified specific genetic changes that may predispose men to this cancer. For example, most testicular cancer cells contain extra copies of a segment of chromosome 12, known as isochromosome 12p (i12p). Variations in genes like KITLG and ATF7IP have also been linked to an increased risk. These genetic insights highlight how subtle alterations in cellular instructions can influence the likelihood of cancer development.
Genome-wide association studies have pinpointed several regions on chromosomes, including 5, 9, and 12, that are associated with an elevated risk. This genetic understanding provides a scientific foundation for the familial patterns observed in some cases.
Dispelling Common Misconceptions
Many misunderstandings exist about what causes testicular cancer. For instance, injury to the testicles, such as from sports or trauma, does not cause testicular cancer. While an injury might draw attention to a pre-existing lump, it is not the underlying cause of the cancer itself.
There is no scientific evidence linking vasectomy to an increased risk of testicular cancer, as this procedure does not alter cellular processes leading to cancer. Similarly, common lifestyle factors like strenuous physical activity, cycling, or wearing tight clothing have not been shown to cause testicular cancer.
Infections are another area of common confusion. Most common infections, including sexually transmitted infections, do not cause testicular cancer. While some evidence suggests a slightly increased risk for men with HIV, and some studies indicate an association with Epstein-Barr virus (EBV), other viruses like HPV and cytomegalovirus (CMV) have not been linked.
Exposure to radiation or certain chemicals is often a concern, but there is no strong evidence directly linking typical environmental or occupational exposures to testicular cancer. While high doses of radiation can increase the risk of some cancers, this is not a common cause of testicular cancer.