Reproductive Tract Tumors in Dogs
Tumors of the Testicles
Testicular tumors are common in male dogs. Most affected dogs are over 6 years of age, with a median age of 10. The majority of tumors occur in undescended testicles-located in the inguinal canal or abdominal cavity. In fact, tumors develop in up to 50 percent of undescended testicles. A swelling or firm mass in the inguinal canal in a dog with an undescended testicle is characteristic of a testicular tumor (although the mass may simply be the undescended testicle).
Tumors in descended testicles are less common. The affected testicle is often larger and firmer than its neighbor and has an irregular, nodular surface. At times the testicle is normal size but feels hard.
The three common testicular tumors in dogs are Sertoli cell tumors, interstitial (Leydig) cell tumor, and seminomas. A small percentage of Sertoli cell tumors and seminomas are malignant.
Some Sertoli cell tumors produce estrogen, which can result in feminization of the male with enlargement of the mammary glands, a pendulous foreskin, and bilateral symmetric hair loss. A serious complication of high estrogen levels is bone marrow suppression.
Ultrasonography is particularly useful in locating undescended testicles and determining whether a scrotal mass is a tumor, abscess, testicular torsion, or scrotal hernia. Fine needle aspiration biopsy provides information on the cell type of the tumor.
Treatment: Neutering is the treatment of choice. This is curative in nearly all cases, even when the tumor is malignant. For scrotal tumors in fully descended testicles, the normal testicle can be left if future fertility is desired. If one or both testicles are undescended, both testicles should be removed, since the condition is heritable and the dog should not be bred. Signs of feminization in Sertoli cell tumors may disappear after neutering-but this is not always the case.
Prevention: Tumors of the testicles can be prevented by neutering dogs early in life. It is particularly important to neuter all dogs with undescended testicles.