Testicular tumours

Testicular tumours are considered one of the most common tumours in older intact (unneutered) male dogs. The overall incidence in dogs is not very high because of the large number of dogs that are castrated. However, in intact male dogs these tumours are considered fairly common. The tumours are usually fairly easy to recognize and diagnose. Treatment consists of castration and is usually curative.
Which dogs are at risk to develop testicular tumours?

Testicular tumours are most common in intact (unneutered) older male dogs. However, they can occur in intact males of any age. There does not appear to be any breed predilection for this tumor. The current cause of testicular tumours is unknown. Dogs that have one or both testicles that are not descended (cryptorchid) are 13 times more likely to develop a tumor in the undescended testicle than dogs with normal testicles. Except for the increased risk of these tumours in cryptorchid dogs, no other risk factors are readily apparent.

Are there different types of testicular tumours?

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.

What are the symptoms?

Sertoli cell tumours show symptoms of swelling of the testicular and scrotal area. If the dog is cryptorchid, the swelling will occur in the inguinal or abdominal area depending on the location of the testicle. Up to 50% of the Sertoli cell tumours will produce estrogen and the dog will suffer symptoms of hyperestrogenism. These include an enlarged prostate gland, enlarged mammary glands and nipples, symmetrical hair loss, anemia, and the tendency to attract other male dogs. Sertoli cell tumours may metastasize to the abdomen, lung, thymus, and brain, however, this occurs in less than 15% of the cases.

Seminomas will also appear as swellings of the testicle, scrotum, and inguinal or abdominal area. Seminomas produce estrogen or metastasize in less than 5% of the reported cases.

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

How are testicular tumours diagnosed?

Diagnosis is based on history, presentation, and pathological identification through a biopsy or microscopic examination of the removed tumor. Dogs suspected of a testicular tumor should also have abdominal and chest x-rays to check for metastasis as well as a chemistry panel and a blood count (CBC).

What is the treatment for testicular tumours?

Treatment usually consists of surgical castration. Because of the success of testicular removal and the low rate of metastasis, castration is often the only treatment needed. Some dogs have been treated successfully with chemotherapy and in dogs that have metastasis, chemotherapy is sometimes recommended.

What is the prognosis for dogs that develop testicular tumours?

The prognosis for dogs with treated testicular cancer is usually very good. The low rate of metastasis makes surgical castration very successful and curative in most dogs. Dogs that develop hyperestrogenism from Sertoli cell tumours will often have a regression of symptoms, once the tumor has been removed. In severe hyperestrogenism that results in anemia, some animals may require transfusions and more aggressive treatment. The prognosis for testicular tumours that have metastasized is more guarded and the outcome varies widely depending on location, type, and treatment.

How can testicular tumours be prevented?

Testicular cancer is easily prevented, and with good castration policies could be virtually eliminated from the canine population.
Testicular tumours are easily prevented through routine castration of male dogs. Castration in young dogs prevents aggression, roaming, urine marking, and a variety of other unwanted male behaviors. The surgery is safe and relatively inexpensive, and in the long run saves the owner money. Dogs that are used for breeding can be castrated when they are no longer used for breeding. Dogs that are cryptorchid should always be castrated and 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. Because the retained testicle is 13 times more likely to develop a tumor, it should always be removed.

© 2005 Drs. Foster and Smith, Inc.
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