Testicular Cancer in Dogs

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Testicular tumors can mostly affect approximately one-third of all intact male dogs across the planet.

In today’s article, we’re looking at the types of testicular cancer that dogs can develop, its causes, symptoms, the way it is diagnosed, and how it can be treated or prevented.

Different Types of Testicular Tumors

There are three main kinds of cancer that affect the testicles of dogs:

  • Seminoma
  • Leydig (also known as interstitial cell tumor)
  • Sertoli cell tumor

Although there is the possibility of a dog developing one type of tumor in one or both of the testicles, there’s also the possibility of the animal having two different types of neoplasms in the two separate testicles.

Other types of neoplasms that affect dogs’ testicles are the following (but their incidence is much lower compared to that of the three we’ve primarily mentioned):

  • Fibroma
  • Lipoma
  • Hemangioma
  • Chondroma
  • Embryonal carcinoma
  • Teratoma


As is the case with any other type of cancer, the exact cause of testicular neoplasms remains unknown. Some dogs might be predisposed to developing testicular cancer genetically.

This disease tends to affect geriatric dogs more than it does young ones – with its incidence being higher in animals that have reached 8 to 10 years of age. Although it is more common in this age category, that does not mean that it cannot affect canine youth, too.

Statistically, dogs whose testicles haven’t descended have a much higher chance of being diagnosed with testicular cancer at one point in their life.

While seminomas and interstitial cell tumors are generally benign, Sertoli cell tumors have a high rate of metastasis.

All of these types of tumors modify the quantity and type of hormones that are circulating in the dog’s bloodstream, for which reason the animal changes his or her behavior. For example, seminomas can affect a dog’s hormone levels to the point that he begins to behave as if he was of the female gender.


Local changes are the clinical signs that you can notice in a dog that has testicular cancer. For example, soft swellings might appear in either one or both of the testicles. Your dog might have asymmetric testicles, but without this being a specific sign of cancer – if they were always like this, it’s probably nothing worth getting worried about.

Skin and hair changes are common, too – brittle hair, hyperpigmentation, and the presence of a red line between the two testicles.

If the dog has a seminoma, you might notice other symptoms, such as the mammary glands being enlarged, elongated nipples, atrophy of the penis, and behavioral changes such as adopting a different position while urinating (squatting instead of hiking a limb).

Some dogs can develop anemia, especially if they suffer from some severe types of testicular cancer, in which cases the bone marrow is affected and the production of red blood cells decreases.

Unfortunately, not all dogs show any symptoms, and not all pet parents are keen on keeping a vigilant eye on that area — which is why they might be diagnosed when the disease has reached a potentially life-threatening stage.


At the vet clinic, some tests will have to be performed in order for the veterinarian to set a clear diagnosis. These may include a complete blood count, biochemistry, imaging tests such as an X-ray or an ultrasound, and in some cases, even a ct scan.

A biopsic exam can prove to be quite useful (histopathology). While in some cases, the masses are removed and then observed under the microscope, the correct procedure is to first find out just what kind of tumor your dog has, and only then decide on the appropriate therapy for it.


There are three main ways of treating cancer in animals at this time. The first is surgery, the second is chemotherapy, and the third is radiation therapy. Unfortunately, radiation therapy can be very painful, and while chemotherapy does have its risks and side effects, it works best alongside surgical castration.

Sometimes, the operation might be a little more complicated, especially if the testicles have not descended and the tumor is located inside the animal’s abdomen.

For cases where the cancer has metastasized, chemotherapy and radiation therapy are almost always performed first, and only then can surgery become an option – if the veterinarian sees that the neoplasm has become well-localized enough to be removed using this treatment method.

What Is the Prognosis for a Dog with Testicular Cancer?

About ten to twenty percent of all cases of testicular cancer in dogs have metastasized by the time they are diagnosed. Therefore, yearly or bi-yearly check-ups at the vet clinic can be essential in making sure that your dog does not develop a severe form of cancer.

Surgery treats approximately all testicular cases. Both Sertoli cell tumors and Leydig tumors have a good prognosis if they have not spread. Seminomas that have not caused any hormonal modifications at the time they are diagnosed also have an excellent prognosis.


Neutering male dogs is the best way of preventing testicular cancer. If the procedure is performed before the dog enters his first heat cycle, it’s even better.

Neutering a male dog whose testicles have not descended is almost mandatory as approximately all such animals develop testicular cancer at one point in their life.

Making sure that your canine friend is healthy by taking him to the vet at least once a year (until the age of 8, twice after) can make it nearly impossible for him to develop severe forms of testicular cancer.



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