Testicular cancer in dogs: how to prevent it

Testicular cancer is relatively common in older dogs that have not been sterilised. It presents as a tumour. Though it is more common in older dogs it can occur in unsterilised males of any age, and in all breeds. The current cause of testicular tumours is unknown.

Dogs that have one or both testicles that are not descended (what is known as ‘cryptorchid’) are 13 times more likely to develop a tumour in the undescended testicle than dogs with normal testicles.

Types of tumour

There are three common types of testicular tumours:

  • Sertoli cell tumours
  • Seminomas and
  • Interstitial cell tumours

While there are differences in the types of tumours, they are often treated similarly and are, therefore, commonly lumped together as testicular tumours.

Signs and symptoms

Sertoli cell tumours show signs of swelling of the testicular and scrotal area.

If the dog is cryptorchid, the swelling will occur in the groin or abdominal area depending on the location of the testicle. Up to 50 percent of the Sertoli cell tumours will produce oestrogen, and the dog will suffer signs of ‘hyperoestrogenism’. These include an enlarged prostate gland, enlarged mammary glands and nipples,  hair loss, anaemia, and the tendency to attract other male dogs. Sertoli cell tumours may metastasize to the abdomen, lung, thymus and brain; however, this occurs in fewer than 15 percent of cases.

Seminomas will also appear as swellings of the testicle, scrotum and groin or abdominal area. Seminomas produce oestrogen or metastasize in fewer than 5 percent of the cases.

Interstitial cell tumours show very few signs and do not produce oestrogen or metastasize. They are usually incidental findings and not considered to be much of a problem.

Your vet will diagnose a tumour after a thorough examination of your dog, taking your pet’s history and a biopsy or microscopic examination of the removed tumour. Dogs suspected of a testicular tumour may also be required to  undergo abdominal and thoracic x-rays to see if the cancer has spread.

Treatment of testicular tumours

Surgical neutering is often the only treatment needed though where a tumour has mestastisized, chemotherapy is sometimes recommended.

The prognosis after treatment is usually very good. The low rate of metastasis makes surgical neutering very successful and curative in most dogs.  In severe hyperestrogenism that results in anaemia, some animals may require transfusions and other treatment.

The prognosis for testicular tumours that have metastasized is more guarded and the outcome varies widely depending on location, type and treatment.

Easy prevention

Testicular cancer is easily prevented through neutering at an early age.

Neutering in young dogs also prevents aggression, roaming, urine marking and a variety of other unwanted male behaviours.

The surgery is safe and relatively inexpensive. In the long term, neutering saves vet’s bills as neutered dogs are usually healthier and less likely to get into fights which may result in injuries. Dogs that are used for breeding can be castrated when they are no longer used for breeding.

Dogs that are cryptorchid should always be neutered. The owner should insist that both testicles be removed.

Since cryptorchidism is considered to be an inherited trait, cryptorchid dogs should never be used for breeding purposes. Because the retained testicle is 13 times more likely to develop a tumour, it should always be removed.


With extracts from an article by Dr Johnny D Hoskins, DVM News.