Testicular Tumors in Dogs

Testicular cancers arise from uncontrolled production of testicular cells and are the most common type of genital tumor in dogs. They are the second most common type of tumor affecting intact males overall.

The three most common types of testicular tumors are seminomas, Leydig cell tumors, and Sertoli cell tumors. Seminomas and Leydig cell tumors are most common.

Seminomas are tumors of sperm producing cells. Seminomas are usually benign but can produce estrogen. Increased estrogen can cause feminization and mammary development.

Leydig cell tumors arise from testosterone producing cells. Leydig cell tumors are small, benign tumors that typically do not cause any symptoms.

Sertoli cells help in sperm development. Sertoli cell tumors spread more frequently than other types of tumors.

Tumors can develop in both testicles and some dogs have more than one type of tumor present.

Many dogs with testicular tumors show no symptoms. Any male pet exhibiting signs of testicular swelling, pain, mammary development, or infertility needs prompt veterinary attention.

Some testicular tumors produce estrogen, a sex hormone.

These tumors can cause secondary symptoms such as

• Mammary (breast) development
• Symmetrical hair loss on the torso
• Hyperpigmentation of skin
• Production of milk

Excessive estrogen can also suppress bone marrow production.

Testicular tumors rarely spread to other areas of the body. Symptoms associated with spread of the tumor will depend on which organ system is involved.

Intact male dogs are the only individuals at risk of developing testicular tumors. Old age and testicles that are retained in the abdomen are significant risk factors for developing testicular cancer.

Testicular cancer is a predisposing factor for testicular torsion.

All forms of cancer are caused by uncontrolled abnormal cell growth. Complex risk factors that include environmental and genetic influences can contribute to uncontrolled cell production. Dogs with undescended testicles are more likely to develop testicular cancers.

Diagnosis includes a physical exam, blood work, urinalysis, imaging, and cytology of the tumor. Biopsy of the mass after castration is needed to confirm diagnosis.

Castration is usually curative as long as the cancer has not spread.

Chemotherapy and radiation may be used for cancer that has metastasized; both have mixed results.

Resolution of testicular tumors is quick with surgery; resolution of symptoms related to excessive estrogen in the system can take 2-6 weeks.

Prognosis is excellent for dogs with no spread or bone marrow suppression. Prognosis is guarded if the cancer has spread or bone marrow suppression is present.

Castration (neutering) prevents testicular tumors. Testicular tumors are not contagious.

Testicular tumors are common in intact males. Undescended testicles are more likely to develop cancer.

• Castration
• Chemotherapy
• Radiation therapy