Testicular Cancer in Dogs 
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To detect testicular cancer in dogs at an early stage, the testicles should be examined regularly by a veterinarian, especially in older male dogs.
Neutered male dogs cannot contract testicular cancer. Discover the likelihood of non-neutered male dogs getting this disease and how dangerous it can be in this article.
Table of contents
How Dangerous Is Testicular Cancer in Dogs?
Testicular tumours are among the most common tumours in non-neutered male dogs — they occur in approximately 16 to 27 percent of the animals examined.
Although testicular cancer in dogs is often benign, testicular tumours can still metastasise or produce hormones that threaten your dog’s health. In the worst case, the cancer can be fatal.
Which Dogs Are Most Often Affected?
Male dogs with normally descended testicles typically develop testicular cancer later in life, usually around ten years of age.
Males with cryptorchidism (undescended testicles) have an almost 14-fold higher risk of the disease. Furthermore, these dogs tend to be affected in midlife.
Symptoms: How Do I Recognise Testicular Cancer in Dogs?
The signs of testicular cancer depend on various factors, including the type, size, and location of the tumour. In addition, testicular tumours in dogs can be hormonally active, which has additional effects.
How Do I Recognise a Testicular Tumour in My Dog?
When the tumour is still very small or the affected testicle has not fully descended, it might not be noticed by the pet owner.
However, as the size increases or the tumour produces hormones (such as androgen or estrogen), the following symptoms may occur:
- the testicles are asymmetrical
- your dog becomes infertile
- it exhibits feminised characteristics (such as hair loss or enlarged mammary glands)
- your dog is prone to the formation of pyogenic ulcers (abscesses) or is susceptible to inflammation of the prostate (prostatitis)
When Should I Go to the Vet?
As soon as your dog exhibits signs of illness, you should consult your vet. This requires you to regularly examine your dog and feel for any changes.
To diagnose a testicular tumour in your dog, the vet will examine and palpate your dog’s testicles. Since testicular tumours differ significantly in echogenicity from healthy testicular tissue, an ultrasound is suitable for excluding non-palpable tumours.
Further examinations
A blood test is also recommended to assess your dog’s health as accurately as possible.
There’s the option to examine a sample using fine-needle biopsy and cytological analysis.
However, many vets avoid this, as the gold standard treatment is the complete removal of the testicles (castration).
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Treatment: How Is Testicular Cancer in Dogs Treated?
The treatment of choice is surgical castration, where the vet removes both testicles, including the scrotum, depending on the type of tumour. If your dog is cryptorchid, the testicular tumour in the abdomen can be removed laparoscopically.
If you wish to preserve your male dog’s fertility, depending on the findings, it may be possible to retain a healthy testicle.
Does Testicular Cancer in Dogs Spread?
Testicular tumours usually develop localised and tend to displace the surrounding tissue in the testicle, but they show little tendency to metastasise to other organs.
On the treatment of metastasising testicular tumours in dogs, there have been few published studies. However, radiation therapy has led to the regression of the tumour in some dogs.
According to studies, chemotherapy (for example, with cisplatin or thalidomide and cyclophosphamide) can also bring temporary improvement.
Prognosis: Is Testicular Cancer in Dogs Curable?
Your dog’s prognosis depends heavily on the type of cancer, whether the tumour is hormonally active, and whether it has already formed metastases.
Leydig cell tumours are almost always benign. Seminomas or Sertoli cell tumours are benign in over 80 percent of cases. However, there are also malignant testicular tumours, which worsen the prognosis. These include especially metastasising inguinal and lumbar lymph nodes.
Note: If your dog suffers from severe aplastic anaemia (anemia), due to high estrogen production, unfortunately, the prognosis is poor.
Causes: What Triggers a Testicular Tumour in Dogs?
Testicular cancer results from the uncontrolled growth of tumour cells in the testicles. The exact cause of testicular cancer in male dogs is unclear.
What Types of Testicular Tumours Occur in Dogs?
The following three types of tumours are the most common causes of testicular cancer in dogs and can also occur simultaneously:
| Type of Tumour | Occurrence | Hormonal Activity | Risk of Metastasis |
| Sertoli cell tumour | particularly common in cryptorchid males | frequent | increased |
| Seminoma | particularly common in cryptorchid males | no | low |
| Leydig cell tumour | no prevalence in cryptorchid males | rare | low |
It is also possible for a chondroma, fibroma, or leiomyoma to be present.
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Prevention: Can Testicular Cancer in Dogs Be Prevented?
The risk of dogs developing testicular cancer increases with age. It is therefore important to regularly palpate your non-neutered male dog.
For early detection, it’s also sensible to have the testicles examined by a vet every year, especially in older dogs.
This article from zooplus Magazine is purely informative. If your pet is experiencing discomfort, contact your veterinarian for diagnosis and treatment.
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At the Justus-Liebig-University of Giessen I was extensively trained as a veterinarian and was able to gain experience in various fields such as small animal, large animal and exotic animal medicine as well as pharmacology, pathology and food hygiene. Since then, I have been working not only as a veterinary author, but also on my scientifically driven dissertation. My goal is to better protect animals from pathogenic bacterial organisms in the future. Besides my veterinary knowledge, I also share my own experiences as a happy dog owner and can thus understand and enlighten fears and problems as well as other important questions about animal health.
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