Seminoma in Dogs

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Overview of Seminoma in Dogs

A seminoma is a tumor of the testicle that involves the germinal cells that normally produce sperm cells. The majority of seminomas are benign, usually slow growing, and not invasive. Five to ten percent are malignant.

The specific cause of tumor development is unknown, but dogs that are cryptorchid, which means that one testicle has not descended into the scrotum, are ten times more likely to develop a tumor. Cyrptorchid testicles are generally within the abdomen, but may be under the skin in the inguinal area, or the area of the body where the hind leg meets the body wall. Cryptorchid testicles are also much more likely to be malignant.

Breeds at greater risk of cryptorchidism such as Weimaraners and Shetland sheepdogs are more likely to develop a seminoma. Boxers are at increased risk of all testicular tumors regardless of cryptorchidism.

Dogs are more likely to develop a seminoma as they age.

Seminomas rarely may produce elevated androgen (male sex hormone) levels or lead to a male feminization syndrome. Seminomas can also cause a severe bone marrow disorder (bone marrow hypoplasia). This is also an unusual occurrence. Most dogs with seminomas are not ill, and many are simply found during a routine physical examination.

What to Watch For

Signs of seminoma in dogs may include: 

  • Soft swellings in one or both testicles
  • A single enlarged testicle or asymmetric testicles
  • Generalized scrotal enlargement
  • Infertility in the breeding stud dog
  • Enlargement of the mammary glands
  • Symmetrical hair loss
  • Hyperpigmentation (darkening or turning black) of the skin
  • Decreased libido and a pendulous prepuce
  • Excessive androgen secretion may also produce signs of prostatic and perianal disease, or diseases around the anus
  • Diagnosis of Seminoma in Dogs

  • A good physical examination including palpation of the testicles
  • Complete blood count (CBC)
  • Platelet count
  • Biochemical profile
  • Urinalysis with or without culture and sensitivity
  • Chest and abdominal X-rays
  • Abdominal and or scrotal ultrasound
  • Fine needle aspiration
  • Biopsy and histopathology (microscopic analysis of tissue) of removed testicle or tumor
  • Treatment of Seminoma in Dogs

  • Surgical removal of the involved testes (orchiectomy)
  • Chemotherapy if the tumor has metastasized (spread)
  • Radiation therapy
  • Supportive care if associated disease conditions are present
  • Home Care and Prevention

    Watch the incision daily for any sign of swelling or discharge. The scrotal sack may be slightly swollen post-operatively, but this should slowly resolve within a week or two. If skin sutures are used, they should be removed in 7 to 10 days.

    If your dog begins to lick the area excessively, an Elizabethan collar may be required to prevent licking at incisions.

    Seek veterinary care if your dog has a fever or is feeling ill post-operatively. If your dog had bone marrow hypoplasia due to the seminoma, close monitoring of blood tests will be required.

    An excellent preventive measure is to have your dog neutered (castrated) at an early age.

    In-depth Information on Seminoma in Dogs

    Usually, seminomas are found as incidental findings on a routine physical exam, or an owner may notice a swelling on the pet’s testicle. Seminomas are often found together with other testicular tumors. They occur in both testicles 10 percent of the time. The majority of the time seminomas cause no clinical problems, but occasionally it may be malignant or cause other serious disease conditions.

    Malignant seminomas usually spread to the lymph nodes of the inguinal (groin) or caudal (toward the tail) abdominal areas. Occasionally they may spread to the lungs. Rarely cryptorchid testicles with seminomas may become large enough to cause abdominal distention and pressure on other abdominal organs. Seminomas may also produce excessive estrogen or, more commonly, elevated androgen production. Changes in androgen or estrogen levels seen with testicular tumors have been associated with prostatic disease that includes prostatic hyperplasia, infection, abscesses, squamous metaplasia, and cyst formation. Elevated androgen levels may also cause perianal disease including perianal adenomas, carcinomas, and perianal hernias.

    Seminomas have also been associated with a male feminizing syndrome. This is caused by changes in hormonal concentrations that result in an elevated estrogen levels that cause the male dog to take on some female characteristics. This occurs more frequently in animals that have Sertoli cell tumors.

    A much more severe and potentially life-threatening condition associated with chronic (long standing) elevated estrogen levels and testicular tumors is estrogen-induced bone marrow hypoplasia. Elevated levels of estrogen have a toxic effect on the bone marrow, and bone marrow hypoplasia may develop where the cells in the bone marrow are damaged and cannot function properly. Since the cells in the bone marrow normally produce red blood cells, white blood cells and platelets that help in clotting, decreases in all three cell lines may be seen (pancytopenia). This may lead to anemia (from the decreased red blood cells), infections (from the decreased white blood cells), and bleeding tendencies (from the decreased platelets).

    Sertoli cell tumors are the most common tumor associated with this condition, but seminomas can occasionally be responsible. Other diseases that have similar clinical symptoms as seminomas include:

  • Interstitial cell tumors and Sertoli cell tumors are other testicular tumors that cause masses on the testes. Both tumors are usually benign, and require aspiration or biopsy to confirm diagnosis.
  • Orchitis and epididymitis are inflammations of the testicle and epididymis, which is the tube-like structure along-side the testicle. They are usually caused by a bacterial infection. The condition generally is painful, and dogs tend to feel ill. Affected dogs may also have a fever. If the infection is severe, the swelling in the testicle may begin to spread up the scrotum and into the inguinal area. Epididymitis may sometimes be caused by Brucella infection
  • Testicular torsion is a twisting of the testicle where blood supply and or lymphatic drainage is compromised. The testicle is usually symmetrically enlarged and painful. The condition is often associated with testicular neoplasia. Testicular torsions occur with greater frequency in abdominal cryptorchid testes.
  • A spermatocele also called a sperm granuloma may occur due to a cyst-like dilation of the epididymis. Sperm may become trapped inside the dilation, and an inflammatory response may occur. This response may produce a small swelling in the epididymis. It is a benign condition, but may result in infertility.
  • An inguinoscrotal hernia occurs when abdominal contents pass into the scrotal sack. Most commonly, it is fatty tissue or a loop of bowel that enters through the inguinal canal. It is not a common condition.
  • If the tumor is located on a cryptorchid testicle and abdominal distention is present, other causes of abdominal swelling would need to be considered, such as other intra-abdominal masses or fluid accumulation.
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