Intact male dogs run a fairly high risk of eventually developing testicular cancer. It's not rare -- on the contrary, it's one of the most common cancers in male dogs. A 2008 study published in the "Journal of Comparative Pathology" showed that 27 percent of intact male dogs had testicular tumors. Fortunately, the prognosis is good for most dogs if the cancer is caught early.
Canine testicular cancer falls into several categories. Sertoli cell tumors usually occur in dogs with undescended testicles. Seminomas form from the inner layers of the testes, while Leydig interstitial cell tumors develop in glands secreting testosterone. It's not uncommon for a dog to have more than one type of tumor.
While any intact male dog can develop testicular cancer, certain breeds are more prone to the disease. These include the Afghan hound, Siberian husky, Shetland sheepdog, fox terrier, Norwegian elkhound, boxer, German shepherd and Weimaraner. Testicular cancer usually appears in older animals.
Dogs with testicular cancer develop a mass or swelling of the testicles. Less often, a feminization process occurs, in which male dogs display certain female characteristics because of excess estrogen. These include nipple and mammary enlargement -- possibly even milk production -- along with penile atrophy. The dog might squat to urinate rather than lift his leg. Other symptoms include hair loss and skin darkening.
Neutering the dog might solve the problem, if the cancer hasn't metastasized. Once a dog no longer has testicles, feminine characteristics generally disappear. Less than 20 percent of canine testicular tumors metastasize. Those that do usually spread to the lymph nodes and on to other organs, primarily the liver, kidneys and pancreas. Dogs with metastatic testicular cancer might undergo chemotherapy.
Neutering your dog is the best way to prevent testicular cancer. If your dog is a cryptorchid, with one or both testicles undescended, it's especially important to have retained testicles surgically removed. Cryptorchid canines run a much higher risk of testicular cancer.
By Jane Meggitt
About the Author
Jane Meggitt has been a writer for more than 20 years. In addition to reporting for a major newspaper chain, she has been published in "Horse News," "Suburban Classic," "Hoof Beats," "Equine Journal" and other publications. She has a Bachelor of Arts in English from New York University and an Associate of Arts from the American Academy of Dramatics Arts, New York City.