Testicular Tumor (Seminoma) in Dogs

Seminomas are fairly rare neoplastic testicular tumors that develop on the testes of intact male dogs. They can be benign or malignant, and they are made up of an overgrowth of cells from the spermatic germinal epithelium. The spermatic germinal epithelium is the innermost layer of the testicle where spermatocytes are produced. Seminomas have a high survival rate with early stage castration surgery. They may also cause an increase in estrogen production and symptoms of feminization including testicular or penile atrophy and mammary enlargement.

Seminoma ar neoplastic testicular tumors made up of an overabundance of spermatic germinal epithelium cells. They are fairly rare and can be either benign or malignant.

Symptoms that may indicate the presence of a seminoma could include:

• Blood in the peritoneal cavity
• Blood in the urine
• Enlarged scrotum
• Infertility
• Spermatic cord torsion (a cord supplying blood to the testicle is twisted)
• Swelling of either or both testicles
• Unexplained growth or tumor on testicles
• Hair loss or poor regrowth
• Brittle hair
• Thinning of the skin
• Darkening of the skin
• Penile atrophy
• Testicular atrophy
• Changes in prostate size
• Mammary enlargement

Excessive estrogen levels can also lead to changes in behavior such as reduced sex drive around females in heat, and squatting to urinate. 

Types 

Three types of cancer will commonly develop on the testes of intact male dogs.

Interstitial (Leydig) cell tumors

• Generally benign tumors of the testes that are composed of an overgrowth of interstitial cells of Leydig, testicular cells that produce testosterone

Seminomas

• Tumors of the testes that are made up of the cells that normally would produce sperm
• These may be either benign or malignant and they often trigger female characteristics in a male dog 

Sertoli cell tumors

• Cancerous tumor made up of the cells that are designed to nurture developing sperm cells
• Sertoli cell tumors are much more common in dogs with undescended testes and are more likely to spread further into the body than the other two testicular cancers

Other less common cancers or growths that can affect the testes can include embryonal carcinomas, gonadoblastomas, granulosa cell tumors, hemangiomas, lymphomas, mucinous adenocarcinomas, rete testis, sarcomas, and teratomas.

The origins of any type of cancer are ambiguous but there are some circumstances that may increase the likelihood of testicular cancers to develop in your male dog. 

• Advanced age
• Exposure to chemicals 
• Infection 
• Radiation exposure
• Undescended testicles
• Dogs with undescended testicles are more than ten times more likely to develop testicular cancer than dogs with normal testes development, and tumors that are located on undescended testicles are more likely to behave malignantly.

Your veterinarian will want to get a verbal history from you as well as a physical examination, including a close examination of the tumors and the area surrounding them. A tissue sample will also be obtained so that it can be microscopically examined. A complete blood count, biochemistry profile, and urinalysis will be acquired to reveal any underlying or concurrent medical issues. The increase in the patient’s level of estrogen will differentiate this type of tumor from Leydig cell tumor as the Leydig cell tumors do not present with increased estrogen

Depending on the size and the placement of the tumor the veterinarian will use either a full excision technique or a fine needle aspiration to take a sample of the tumor. The biopsy of this tissue will reveal the source of the cells in the growth. An ultrasound of the testicle and abdomen area may also be recommended to get a better idea of the size, placement, and shape of the testes within the body.

The first course of action with any testicular tumors is surgical removal of the testicles. It is often recommended that the scrotal skin be removed as well to avoid post-operative pain and swelling and it is often necessary to remove a portion of the spermatic cord as well. If the testicle or testicles have not dropped the surgery may involve abdominal surgery as well to access the testicles for removal. Surgery is completely curative for a majority of Seminoma cell tumors as the metastatic rate is low. In the event that the tumor spreads more aggressive steps may be required to prevent reoccurrence. Radiation therapy and chemotherapy treatments are often employed in those circumstances and the prognosis becomes more guarded and varies based on location and treatment options available. Chemotherapy alone has been endorsed as an alternative for these growths in those rare situations in which surgery is not an option.

After any surgery, it is essential to keep the site clean and free from dirt and debris. You will need to keep your pet from interfering with the site, and examine it often over the next two or three weeks for swelling, bleeding or pus. Keeping the recovering patient in a calm, quiet environment will help encourage healing, as will having appropriate food and water within their reach.  Specialized feeding and care instructions may be given by your veterinarian to facilitate healing and you may need to bring your pet back in to evaluate healing in about ten to fourteen days. Once your pet has recovered your veterinarian may want to reevaluate him for recurrence or metastasis in the case of a malignant tumor.