Testicular cancer in male dogs: causes, diagnosis & treatment

Testicular cancer is a common health concern in unneutered (intact) male dogs, especially as they age. It occurs due to abnormal growths or tumours developing in one or both testicles where testosterone is produced. Because neutered males no longer have testes, they cannot develop this condition. In veterinary practice, testicular tumours are frequently diagnosed in mature male dogs, particularly over four years old.

If you own an unneutered dog, understanding the risks, types, diagnosis, and treatment options is crucial for responsible ownership and canine health.

What types of dogs can develop testicular cancer?

Only unneutered male dogs are at risk of testicular cancer. Female dogs and neutered males do not develop these tumours. The condition typically affects adult dogs aged four or older. There is no strong breed predisposition, so all breeds are equally susceptible. However, dogs with cryptorchidism — meaning one or both testicles have failed to descend into the scrotum and remain inside the abdomen or groin — have over ten times the risk of developing cancer in the retained testicle compared to normally descended testes.

Responsible breeders and owners monitor cryptorchid dogs closely and are encouraged to neuter these dogs early to prevent testicular cancer development.

Common types of testicular tumours in dogs

There are three main types of testicular tumours, each originating from different cells in the testicle. Despite their differences, treatment generally involves surgical removal.

Sertoli cell tumours

These tumours cause swelling in the scrotum or, in cryptorchid dogs, the abdomen or inguinal (groin) area. Sertoli cell tumours produce oestrogen, leading to hormonal imbalances in about half of affected dogs. Symptoms include enlarged prostate, hair loss, anaemia, swollen nipples, and enlarged mammary glands. There is a risk of metastasis (spread) to lungs, brain, or abdomen, but this is uncommon.

Seminomas

Seminomas cause generalised swelling of the testicles and surrounding areas. Although capable of producing oestrogen and spreading, metastasis occurs in less than 5% of cases. Early detection often leads to a good prognosis.

Interstitial cell tumours

Usually discovered incidentally, these tumours cause no obvious symptoms and rarely spread or produce hormones. They are generally considered low risk and less concerning clinically.

How is testicular cancer diagnosed by a vet?

Your vet will take a detailed history and perform a physical examination focusing on the testicles. If a mass or swelling is found, diagnostic tests such as biopsy, ultrasound, and blood tests are used to confirm the diagnosis. X-rays of the chest and abdomen may be taken to check for any spread (metastasis).

How is testicular cancer treated in dogs?

Fortunately, testicular cancer in dogs is usually straightforward to treat. Castration (orchiectomy) removes the affected testicle(s) and is generally curative. Since testicular tumours rarely spread, surgery alone often suffices.

In cases where metastasis is present or if the dog is a poor surgical candidate, chemotherapy may be recommended alongside or instead of surgery to manage the disease.

What is the prognosis after treatment?

Dogs treated with castration typically have an excellent prognosis, with close to 100% survival rates when tumours are detected early. Recovery from surgery is usually quick and uneventful.

When metastasis has occurred, treatment is more complex and the prognosis is more guarded. Some tumours producing excess oestrogen can cause anaemia and require additional treatments such as blood transfusions.

Can testicular cancer in dogs be prevented?

Yes. Preventing testicular cancer is simple and effective through early neutering. Neutering removes the testes before tumours have a chance to develop. This is particularly important for cryptorchid dogs who are at significantly higher risk.

Protecting your dog with responsible neutering not only prevents testicular cancer but also contributes to overall canine health and longevity.

For new owners looking for a future dog to add to your family, the puppies for sale section is a great place to find responsibly bred puppies. Choosing a reputable breeder or adopting from shelters ensures you support ethical dog ownership and promote healthy, happy pets.

What age is best to neuter a male dog to prevent testicular cancer?

Quick Answer: The best age to neuter male dogs to prevent testicular cancer is typically between six to twelve months. Neutering before sexual maturity significantly lowers cancer risk and prevents other reproductive health problems.

Neutering before the first heat or sexual maturity (usually by six months of age) is widely recommended. This timing prevents hormone-driven tumours like testicular cancer. Talk to your vet about the optimal timing based on your dog's breed, size, and health status to ensure safe and effective surgery.

How common is testicular cancer in male dogs?

Quick Answer: Testicular cancer is one of the most common tumours in intact male dogs, with studies suggesting up to 27% may develop testicular tumours during their lifetime, especially in older dogs over seven years old.

The risk increases significantly with age and is notably higher in cryptorchid dogs. Early neutering virtually eliminates this risk. Regular vet check-ups help detect early signs to improve treatment success and survival rates.