How Common is Testicular Cancer in Dogs?

Testicular cancer in dogs is described as the abnormal growth of cells in a dog’s testicles. It is among the most common types of cancer affecting intact (unneutered) male dogs, particularly as they age. While many cases are benign and slow-growing, some can be aggressive and lead to significant health complications if left untreated. Certain breeds and dogs with undescended testicles (cryptorchidism) face a higher risk. This makes awareness and early detection crucial. Clinical signs of testicular cancer can range from subtle changes in testicular size to systemic effects caused by hormonal imbalances. Understanding the types, prevalence, and treatment options for testicular tumours enables dog owners to make informed decisions about their pet’s health and well-being.

How Common is Testicular Cancer in Dogs?

A frequently mentioned reason for neutering male dogs is to eliminate the risk of testicular cancer. While this concern is valid, it is important to consider the broader picture. Compared to other canine cancers, testicular cancer is relatively uncommon, though it can still pose a health risk. Research indicates that testicular tumours make up around 4-7% of all tumours diagnosed in intact male dogs. Although the overall risk is low, the chances of developing testicular cancer increase with age, with most cases occurring in dogs older than seven. Certain breeds, such as Boxers, German Shepherds, Afghan Hounds, and Shetland Sheepdogs, may be more susceptible to these tumours. Additionally, dogs with cryptorchidism—a condition where one or both testicles remain undescended—face a significantly higher risk. This is because retained testicles are exposed to higher body temperatures. This may disrupt the normal development of the testicle which can contribute to abnormal cell growth and tumour formation. While testicular cancer is not exceedingly common, it remains a concern for unneutered dogs, highlighting the importance of regular veterinary examinations for early detection and treatment.

Types of Testicular Cancer in Dogs

Dogs, like humans, can develop various types of testicular tumours. The three most common types are:

Seminomas

Arising from the pre-sperm stem cells within the testes, seminomas are generally benign, though they can occasionally become malignant. They tend to occur in older, intact male dogs and can cause testicular enlargement or discomfort.

Sertoli Cell Tumours

These tumours develop from the Sertoli cells, which support sperm production. Sertoli cell tumours can be benign or malignant and may lead to a condition known as feminisation syndrome, where oestrogen production increases. This can cause symptoms such as hair loss, enlarged mammary glands, and behavioural changes.

Leydig (Interstitial) Cell Tumours

These are the most common testicular tumours in dogs but are often benign and rarely cause clinical symptoms. They develop from Leydig cells, which produce testosterone.

Each of these tumours can vary significantly in their impact on the overall health of the dog.

Clinical Signs of Testicular Cancer in Dogs

Testicular tumours in dogs often present with subtle signs, which is why they can go unnoticed for a long time. Dog owners should be aware of the following potential indicators:

Enlargement of one or both testicles. This can be a noticeable swelling or a subtle change in size.
Asymmetry. One testicle may appear different to the other. This could be larger, firmer or a different colour.
Pain and discomfort. Some dogs may show signs of pain when the affected testicle is touched or when they are sitting or lying down.
Changes in skin or coat. There may be generalised thinning of the hair or symmetrical hair loss due to hormonal imbalances.
Feminisation syndrome. This can include enlargement of mammary glands, behavioural changes, darkening of some areas of the skin and sudden attraction to and from other male dogs. It is usually caused by excess oestrogen.
Weight loss and lethargy. More advanced cases of testicular cancer can lead to systemic illness if the cancer spreads. This can manifest as weight loss and lethargy amongst other things.
Blood disorders. In severe cases, bone marrow suppression from excessive oestrogen can cause anaemia, increasing susceptibility to infections and bleeding disorders.

Given the subtle nature of early symptoms, routine veterinary check-ups are essential for intact male dogs, particularly as they get older.

Diagnosis of Testicular Cancer

Diagnosing testicular cancer in dogs typically involves:

Physical Examination

Your vet will examine your dog thoroughly, from nose to tail. They will palpate the testicles to check for things like asymmetry, swelling, or any firm masses.

Lab Tests

Blood tests can be carried out to detect hormonal imbalances or signs of systemic illness caused by tumour-related complications, as well as checking organ function and blood cell counts. Urinalysis can be useful in helping diagnose issues too.

Ultrasound of the testicles

Scanning can help assess the structure of the testicles and identify any abnormal growths.

X-rays and Ultrasound of the Abdomen

If a malignant tumour is suspected, imaging may be used to check for the spread of the cancer in the abdomen or other areas. Ultrasound and X-ray can also be used to detect cryptorchid testicles if they are situated in the abdominal cavity.

Fine Needle Aspiration (FNA) or Biopsy

In some cases, a small sample of the tumour is taken for microscopic analysis. This can be done using a fine needle or by surgically removing a small piece of tissue while the dog is under general anaesthetic.

Severity and Risks Associated with Testicular Cancer

The severity of testicular cancer in dogs varies depending on the type of tumour and whether it has spread (metastasised). Fortunately, many testicular tumours are benign, meaning they remain localised and do not spread to other organs. However, certain cases do pose risks. Seminomas and Sertoli cell tumours have a low metastatic potential meaning they rarely spread to other body parts.

Sertoli cell tumours may cause a condition called hyperestrogenism. This can suppress bone marrow function and lead to anaemia, a serious and potentially life-threatening complication. Interstitial cell tumours are usually benign and remain confined to the testicles.

In addition, some cancers can affect the testicles from other parts of the body. Some originate in the reproductive or urinary tract and spread to the testicles. In these cases, if metastasis has occurred, the severity of the cancer and the prognosis for the dog will depend on factors such as the tumour type, its location, and the available treatment options. While the majority of testicular tumours are not aggressive, the possibility of complications reinforces the importance of early detection and intervention.

Treatment Options and Prognosis

The primary treatment for testicular cancer in dogs is surgical removal of the affected testicle(s), a procedure known as castration (orchidectomy). In most cases, neutering alone is curative, particularly if the tumour is benign and localised.

For malignant tumours or cases where metastasis is suspected, additional treatments may include:

Chemotherapy. This is used in cases where the cancer has spread beyond the testicles.
Radiation Therapy. This is rarely required but may be beneficial in certain aggressive cases.
Supportive Care. Blood transfusions or hormone therapy may be necessary in dogs experiencing severe complications like bone marrow suppression.

The prognosis for dogs with testicular cancer is generally excellent, especially when diagnosed early and treated surgically. Even in cases where malignancy is present, many dogs can still have a good quality of life with appropriate management.

Does Neutering Prevent Testicular Cancer?

Yes, neutering completely eliminates the risk of testicular cancer, as the testicles are removed before tumours can develop. This is one of the reasons why neutering is often recommended, particularly for high risk breeds or dogs with cryptorchidism. However, given that testicular cancer is not exceedingly common and is often treatable, it should not be the sole reason to neuter a dog.

Neutering also has additional benefits, including reducing the risk of benign prostatic hyperplasia (BPH) and eliminating behaviours such as roaming, marking, and aggression driven by testosterone. However, neutering is not without potential drawbacks, such as a slightly increased risk of obesity and certain joint conditions, particularly if done at a very young age. Your vet will discuss all the pros and cons of the surgery with you in detail.

Conclusion

Testicular cancer in dogs is an important health consideration but it is not overwhelmingly common. While it is true that neutering eliminates the risk, most testicular tumours are benign and treatable with surgery. Pet owners should weigh the benefits of neutering against other health considerations and make informed decisions based on their dog’s individual needs. Regular veterinary check-ups are key to detecting testicular tumours early, ensuring successful treatment and a good prognosis. If you have concerns about your dog’s health, particularly regarding testicular changes or hormone-related symptoms, consult your vet for advice, they will always be happy to help. By staying informed and proactive, pet owners can ensure the best possible care for their furry companions, whether they choose to neuter or not.

How Common is Testicular Cancer in Dogs?