Signs & symptoms of testicular cancer in dogs

Updated April 17, 2017

Testicular cancer is common in male dogs who have not been castrated. It is more common in older dogs, but can occur at any age. There are three different kinds of testicular tumours: Sertoli cell tumours, seminomas and interstitial cell tumours. Testicular cancer spreads to other parts of the dog in an average of only 15 per cent of cases. Fortunately, testicular cancer can be easily treated if you recognise the symptoms and catch the cancer before it spreads.

Uneven Size of Testicles

If you notice that one of your dog's testicles is larger than the other it may be caused by swelling due to a tumour. Examine your dog closely for soft or hard lumps that may be enlarging his testicle. Dogs who have an undescended testicle have a 13 per cent greater probability of developing cancer. Look for swelling in the scrotum or abdomen if your dog's testicles are undescended.

Blood in the Urine

Testicular cancer can also cause bleeding when your dog urinates. You may notice that your dog squats when eliminating, or that the colour of his urine becomes darker. This symptom is linked to a variety of illnesses, so you will want to have your vet confirm a diagnosis of testicular cancer by conducting abdominal and thoracic X-rays.


Some testicular cancers will cause an increased production of the female hormone oestrogen. This hormone imbalance will produce visible symptoms like enlarged breasts and nipples, or hair loss on both sides of the body. Your dog may also begin to attract other male dogs.


If you notice any of these symptoms take your dog to the veterinarian for a biopsy and blood work. Neutering your dog is usually the only treatment needed, and long term prognosis for dogs treated for testicular cancer is very good.

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About the Author

Lori Karnac is a librarian, researcher and professor who has done academic research and writing since 1990. Karnac has written for the Key West Arts blog and "Artlurker" in Miami. She has a Master of Arts in library and information sciences from the University of California at Berkeley, and teaches academic research, art and design classes.