Testicular cancer does not usually have one single clear cause, but several risk factors are known to raise the chance that it develops.

Key idea: “Causes” vs “risk factors”

Doctors don’t yet fully understand why a normal testicular cell turns cancerous in one person but not another.

Instead, they focus on factors that make cancer more likely (risk factors), some of which you can’t change (like family history) and some that relate to health or environment.

Strongest known risk factors

These are the best‑established factors linked to a higher risk of testicular cancer:

  • Undescended testicle (cryptorchidism) : If a testicle did not move down into the scrotum before birth or in early childhood, the risk of cancer in that testicle (and sometimes the other) is several times higher, even if surgery later brought it down.
  • Previous testicular cancer : Having had cancer in one testicle raises the chance of developing it in the other.
  • Family history : Having a father or brother with testicular cancer significantly increases risk, suggesting a genetic component.
  • Certain congenital or developmental abnormalities : Abnormal testicle development and conditions like hypospadias (abnormal opening of the urethra on the penis) are associated with higher risk.

Other medical and genetic factors

Research has also linked several other medical conditions to increased risk:

  • Infertility and testicular atrophy : Men with infertility or smaller, underdeveloped testicles have a higher incidence of testicular cancer.
  • HIV infection (especially AIDS) : HIV‑positive men, particularly with AIDS, have higher rates of testicular cancer.
  • Certain genetic syndromes : For example, Klinefelter syndrome and some hereditary cancer syndromes may increase risk.
  • Prior inflammation/infection of testicle (epididymo‑orchitis) : Some studies show markedly higher cancer risk in men who previously had severe inflammation of the testicle and epididymis.

Early‑life and perinatal influences

Because testicular cancer often appears in young adults, factors around birth and childhood may play a role:

  • Low birth weight, twinning, and perinatal inguinal hernia : These have all been statistically associated with higher testicular cancer risk.
  • Hormonal exposures before birth : Exposure in the womb to certain synthetic estrogens such as diethylstilbestrol (DES) has been linked to increased risk.

These don’t “cause” cancer by themselves, but may set the stage for abnormal testicular development.

Lifestyle and environmental factors (evidence weaker)

Some factors are under active study; evidence is suggestive but not as strong:

  • Smoking and cannabis use : Both tobacco and cannabis smoking have been associated with a higher risk in some studies, but results are not fully consistent.
  • Diet : High intake of dairy products, red meat, and certain baked foods has been linked with slightly higher risk in questionnaire‑based studies.
  • Occupational and chemical exposures : Work as a firefighter and exposure to pesticides (such as DDT), certain solvents (like DMF), and industrial chemicals like PFOA have been reported as possible risk factors.
  • Electromagnetic fields : A few small studies have suggested a possible link, but data are limited and not conclusive.

Scientists treat these as “possible” or “probable” risk factors, not proven direct causes.

Who gets testicular cancer more often?

Patterns in who is affected give clues about underlying causes:

  • Age : It’s most common in younger men, especially about 20–40 years old; non‑seminomas peak around 25–29, seminomas around 35–39.
  • Ethnicity : White men (particularly of European ancestry) have higher rates than men of many other ethnic backgrounds.
  • Height : Being unusually tall as an adult has been linked to a slightly higher risk.

These patterns suggest genetic and early‑development influences, but they don’t point to a single clear cause.

What does not usually cause it?

  • Everyday minor bumps or injuries to the testicles are not known to cause cancer, although they may draw attention to a lump that was already there.
  • Having a vasectomy is not considered a cause of testicular cancer.

Simple takeaway and what to do

  • Most cases of testicular cancer happen without any obvious risk factor you can pinpoint.
  • The most important thing you can do is notice changes early: a painless lump, swelling, heaviness, or change in size or feel of a testicle should be checked promptly by a doctor.

If you have specific concerns (for example, undescended testicle history, infertility, or family history), a urologist can discuss your personal risk and whether any regular follow‑up is sensible.

TL;DR:
Testicular cancer likely arises from a mix of genetic susceptibility, abnormal testicular development (especially undescended testicle), and certain medical, hormonal, and possibly environmental exposures, but in many men no clear cause is ever found.

Information gathered from public forums or data available on the internet and portrayed here.