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.

    In-depth Information on Diagnosis

  • Complete physical examination. All intact male dogs should have their testicles palpated as part of their routine physical exam. Most seminomas are found incidentally during the exam, since most dogs do not display any symptoms of illness. On the other hand, dogs with the feminization syndrome have typical physical exam changes that suggest a hormonal cause of the problem.
  • CBC. The CBC evaluates the red and white blood cells. The test is especially useful if a seminoma is causing bone marrow hypoplasia. Decreased red cell counts (anemia) and low white cell counts can be expected in this serious condition. The reticulocytes – young, recently released red cells from the bone marrow – might be counted to determine whether the bone marrow was responding to the anemia appropriately by producing new young red cells. The reticulocyte count is low (non-regenerative) if the anemia was due to estrogen toxicity. The only way to confirm the diagnosis of bone marrow hypoplasia is through a bone marrow aspirate and microscopic evaluation of the cell types.
  • Platelet count. Just as the red and white cell lines are decreased with bone marrow hypoplasia, the platelets, which are also produced in the bone marrow, may also be decreased. This test is especially important to run if any excessive bleeding or bruising is noted.
  • Biochemical profile. The biochemical profile evaluates for liver or kidney disease, diabetes, and changes in electrolytes. Since most dogs with seminomas are older, it is a valuable screening test for other concurrent diseases. If the tumor is malignant, and has metastasized (spread), elevations in liver enzymes might be noted. Additionally, all animals that are to undergo a surgical procedure should have a biochemical profile done as part of their pre-operative blood work.
  • Urinalysis. If the testicular swelling is caused by an infection, a urinalysis with a culture and sensitivity might show bacteria and an increased white blood cell count. A urinalysis is also needed to assess kidney function.
  • Even though seminomas are rarely malignant, chest X-rays are recommended to determine if the tumor has spread to the lungs. In older animals it is also a good pre-operative screening test to evaluate for evidence of cardiac disease or other pulmonary conditions. In the cryptorchid dog, abdominal X-rays are taken, as many larger tumors may be easily visualized. Abdominal X-rays are also useful in evaluating the size and shape of other abdominal organs. Occasionally, with metastatic disease, the lymph nodes under the lumbar vertebrae may be enlarged and visible radiographically.
  • An abdominal ultrasound is useful to better identify a mass within the abdomen as can be seen with a cryptorchid seminoma. The rest of the abdomen can also be checked for signs of tumor spread and other organ involvement. In non-cryptorchid dogs, generalized scrotal swelling is sometimes present. This may prevent accurate identification of a specific mass. A scrotal ultrasound is an excellent test to determine if a tumor is present in a swollen scrotum.
  • With the aid of ultrasound, an abdominal mass can be aspirated by fine needle. The collected cells are then examined microscopically (cytology). A fine needle aspirate is generally a safe and effective method of tissue evaluation, but it may not be diagnostic, since only a small amount of cells are collected. Intra-scrotal testicular masses generally do not require ultrasound for aspiration.
  • A biopsy provides a better sample as a core of tissue is obtained for microscopic examination (histopathology). More accurate information is usually obtained since a larger amount of tissue can be evaluated. Cryptorchid testicles have biopsies using ultrasound as a guide or at surgery. Most times the biopsy is combined with the full removal of the entire tumor, which is called an excisional biopsy. Based on the previous diagnostics, it is not always needed to biopsy a tumor prior to its removal.
  • In-depth Information on Treatment

    The vast majority of dogs with seminomas have an excellent prognosis. However, since there is a higher incidence of malignancy in cryptorchid tumors, a more aggressive work-up and treatment is required. Some animals may experience acute abdominal pain due to a testicular torsion (associated with a cryptorchid seminoma) and may require rapid intervention. Dogs that have the male feminization syndrome have a good prognosis, as long as there is no evidence of malignancy or bone marrow disease. Animals that have bone marrow hypoplasia due to estrogen toxicity must be treated aggressively, although they tend to do poorly. Specific treatment for seminomas include:

  • Orchiectomy (castration). The treatment of choice for seminomas, either scrotal or cryptorchid is the surgical removal of the affected testicle. Both testes are removed due to the high incidence of tumors involving both testicles. Cryptorchid testicles often require major abdominal surgery, and a more prolonged hospital stay. A complete evaluation of all internal organs should be done at surgery to check for evidence of metastatic disease. The vast majority of dogs with seminomas have no evidence of tumor spread at the time of diagnosis and orchiectomy is curative.
  • Chemotherapy for metastatic seminomas might be considered, although there is limited experience in its use in dogs.
  • Radiation therapy is probably the best treatment option for metastatic disease, but again experience is limited. Seminomas in people are very sensitive to radiation therapy, and in the limited number of cases in dogs, radiation therapy also seems to be an effective treatment option. Radiation therapy usually requires referral to a specialty practice or academic institution.
  • Dogs that have bone marrow hypoplasia may be quite ill and require significant care. Therapy for anemia, infection, and potential bleeding problems needs to be addressed. Intravenous fluids, broad-spectrum antibiotics, and blood or platelet transfusions may be needed to stabilize the patient prior to the surgical removal of the tumor. Bone marrow stimulating factors may also be used in an attempt to speed the recovery of the bone marrow cells, although its efficacy is uncertain. Specifically, erythropoietin (EPO) is used to stimulate the red blood cell lines and granulocyte colony-stimulating factor (G-CSF) may be used for the white blood cell lines. Multiple blood transfusions may be needed to sustain an animal before the bone marrow recovers. Signs of bone marrow improvement may take 3 to 6 weeks, but may not be normal for several months. Unfortunately, most animals with bone marrow involvement do not respond to therapy.
  • Follow-up Care for Dogs with Seminoma

    Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not improve rapidly.

  • Administer all medications as directed. Alert your veterinarian if you are experiencing problems treating your dog.
  • The incision and scrotum should be checked daily for any signs of swelling or discharge. Occasionally blood may ooze into the scrotum postoperatively causing a scrotal hematoma (blood clot). Scrotal hematomas may become quite large and can be painful, but they usually resolve on their own.
  • Routine castrations usually do not require antibiotics, but if there is a significant amount of discharge from the incision or swelling, infection may be present and antibiotics advised.
  • If bone marrow disease was present, a CBC and platelet count should be followed closely looking for improvement in the red and white blood cell counts as well as platelets. Prophylactic antibiotics may need to be given long term, while the white blood cell counts are depressed, in an attempt to decrease the incidence of infection.
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