Testicular cancer is a malignancy that begins in the testicles, the male reproductive glands located in the scrotum. While a singular, definitive cause remains unknown, research indicates the cancer arises from specific cellular abnormalities. The condition is strongly linked to several established biological processes and certain inherited or medical risk factors. Understanding these underlying cellular mechanisms and susceptibility factors is important for addressing the disease’s etiology.
The Role of Germ Cells in Development
Nearly all testicular cancers (over 90%) originate in the germ cells, which are responsible for producing sperm. This suggests the cancer begins with a malfunction in the reproductive cell line early in development. The resulting tumors are classified into two main types: seminomas and nonseminomas. Seminomas are slower-growing and typically diagnosed in men in their late 30s and early 40s.
Nonseminomas, such as embryonal carcinoma and teratoma, generally grow and spread more rapidly. They often affect younger men in their late teens to early 30s. The malignancy frequently stems from a precursor condition called Germ Cell Neoplasia In Situ (GCNIS). GCNIS involves abnormal germ cells confined to the seminiferous tubules inside the testicle.
These abnormal GCNIS cells look like cancer cells but are not yet invasive. Approximately 50% of men diagnosed with GCNIS will progress to invasive testicular cancer within five years if untreated. The progression occurs when these cells break out of the seminiferous tubules and spread into the surrounding testicular tissue.
Established Medical and Genetic Risk Factors
The most significant risk factor identified is cryptorchidism, or having an undescended testicle. During fetal development, the testicles typically form in the abdomen and descend into the scrotum before birth. A failure to descend increases the likelihood of cancer development by three to eight times compared to the general population.
The risk is higher if the testicle remained in the abdomen rather than having descended partially into the groin. However, the non-descent itself is likely not the cause, but rather an indication of an underlying abnormality in the testicle that makes it prone to cancer. Corrective surgery, called orchiopexy, may reduce the cancer risk slightly, but it does not eliminate it completely.
A personal history of testicular cancer in one testicle raises the risk of developing the disease in the other, occurring in about 3% to 4% of men. Genetic susceptibility plays a role, with the risk increasing if a close relative has had the disease. Men with a brother who had testicular cancer face an eight- to twelvefold increase in risk, while having an affected father results in a two- to fourfold increased risk.
Testicular cancer is the most common cancer in males between the ages of 15 and 35. The disease also shows a strong racial disparity, as white men are four to five times more likely to develop testicular cancer than Black or Asian-American men. Certain congenital syndromes, such as Klinefelter syndrome, which involves an extra X chromosome, are also associated with a greater risk.
Factors That Do Not Cause Testicular Cancer
Many common beliefs about the causes of testicular cancer are not supported by scientific evidence. Trauma or injury to the testicles, such as a sports-related impact, has not been proven to cause the disease. While injury may cause temporary pain or swelling, it does not initiate the cellular changes that lead to malignancy.
Similarly, common lifestyle choices and habits do not appear to influence risk. Wearing tight underwear or tight-fitting jeans does not increase the risk of developing testicular cancer. The theory that tight clothing could cause cancer by increasing scrotal temperature is not backed by high-level scientific evidence.
There is also no demonstrated association between having a vasectomy, a surgical procedure for male sterilization, and an increased incidence of testicular cancer. Cohort studies involving tens of thousands of men have shown that the rate of testicular cancer in men who have had a vasectomy is no higher than in the general male population.