Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut elit tellus, luctus nec ullamcorper mattis, pulvinar dapibus leo.

Testicular Tumors in Dogs

What Are Testicular Tumors in Dogs?

Testicular tumors are prevalent among older unneutered male dogs and rank as one of the most commonly encountered tumors. These dogs retain both testicles, which serve in sperm production for reproduction and the secretion of male hormones like testosterone.

Tumor formation occurs when cells undergo abnormal growth, proliferating and dividing uncontrollably, resulting in an abnormal tissue mass. If left untreated, the mass may continue to grow and expand. Testicular tumors are relatively uncommon, primarily because many dogs undergo neutering at a young age.

Tumors can either be benign or malignant. A benign tumor diagnosis indicates that it is non-cancerous and has not metastasized beyond its original location, such as outside the testicle. On the other hand, a tumor is deemed malignant when it is cancerous and has spread from its original site, such as a mass originating in the testicle and spreading to other organs like the lungs and lymph nodes.

Types of Testicular Tumors in Dogs

Male dogs can develop three primary types of testicular tumors:

  • Seminoma – These tumors originate from the cells responsible for sperm production, also known as “germ cells.”
  • Interstitial cell tumors – These tumors arise from the cells that produce testosterone.
  • Sertoli cell tumors – These tumors develop from Sertoli cells, which provide nourishment and support to developing sperm.

While other forms of testicular tumors such as lipomas, fibromas, and hemangiomas are possible, they are rare occurrences in dogs.


Detecting testicular tumors in dogs can be challenging as clinical signs may not always be apparent and can vary based on the tumor’s type and location. In dogs with longer coats, the testicles may be obscured by hair, making them difficult to observe. Typically, testicular tumors are discovered during a physical examination when the testicles are palpated for any abnormalities.

Symptoms may include:

  • Presence of one or multiple enlarged nodules visible or felt within the affected testicle(s)
  • Variation in testicular size
  • Swelling of the scrotum (the sac containing the testicles)
  • Enlarged mammary glands and nipples
  • Drooping prepuce (the sheath of the penis)
  • Hair loss and darkening of the skin
  • Squatting posture during urination (similar to female dogs)
  • Infertility in male dogs intended for breeding
  • Increased sexual attraction from other male dogs due to elevated estrogen levels

If the tumor has metastasized beyond the testicle, additional symptoms may include:

  • Lethargy beyond the usual level of tiredness
  • Weight loss
  • Decreased appetite
  • Difficulty breathing or labored breathing
  • Coughing
  • Difficulty urinating and/or defecating due to enlarged lymph nodes or compression of the prostate gland narrowing or obstructing these passages.

What Does a Testicular Tumor Look Like?

Normal testicles have an egg-shaped appearance and are situated within the scrotum, positioned between the upper thighs and behind the penis. It’s common for one testicle to be slightly higher than the other.

Signs indicating a potential tumor in the testicles or scrotum include:

  • Soft or firm swelling affecting one or both testicles
  • Enlargement of the scrotum
  • Noticeable size difference between the two testicles
  • Asymmetry in the appearance of the testicles
  • Irregular, lumpy, or bumpy texture of the testicles
  • Sensitivity or pain in the affected testicle(s)


The exact reasons why some dogs develop testicular tumors while others do not remain unclear, but certain environmental, genetic, and breed-related factors may contribute as risk factors.

Age is considered a significant risk factor. Although testicular tumors can occur in unneutered dogs of any age and breed, they are most frequently observed in dogs over 10 years old. Additionally, breeds such as the German Shepherd, Afghan Hound, Boxer, Weimaraner, and Collie are particularly prone to developing these tumors.


Discovery of a testicular tumor may occur incidentally during a routine physical examination. Your veterinarian might detect an unusual nodule or texture distinct from normal testicular tissue, or they may notice the absence of one testicle, a condition known as cryptorchidism, which affects around 13% of male dogs.

If your dog exhibits signs of illness and a tumor is suspected, your veterinarian may suggest chest or abdominal x-rays, or an abdominal and scrotal/testicular ultrasound to identify any masses. Additionally, bloodwork, urinalysis, and a rectal examination may be conducted to detect any potential abnormalities.

Definitive diagnosis of the tumor type occurs post-surgery, where a sample of the abnormal tissue is sent to a veterinary pathologist for laboratory examination. This step is crucial for determining the tumor’s type and whether it is benign or malignant.

For breeding dogs, your veterinarian might consider a small biopsy of the abnormal tissue or a fine needle aspirate (a tissue sample obtained with a small needle) as an alternative to neuter surgery to ascertain the tumor type.


The primary treatment for testicular tumors in dogs involves surgical removal of the affected testicles. In cases where the tumor is malignant and has spread beyond the testicles, additional therapies like chemotherapy or radiation therapy may be employed to halt the progression of cancer.

Various complicating factors, such as underlying diseases, heart murmurs, respiratory problems, or obesity, may render a dog unsuitable for anesthesia and surgery.

In instances where a tumor is diagnosed as benign and remains small and slow-growing, it may be possible to monitor it until negative changes occur, such as enlargement, pain, bleeding, or interference with the dog’s mobility. However, tumors are typically removed well before they cause discomfort to the dog.

Recovery and Management

Testicular tumors typically exhibit a low rate of metastasis if they are cancerous, and surgical removal of the testicles often resolves the issue.

Sertoli cell tumors and seminomas carry a metastasis probability of less than 15%, while interstitial cell tumors are typically benign and seldom extend beyond the testicles. However, cancers originating in the urinary or reproductive tract may potentially spread to the testicles, necessitating thorough examination of other tissues and organs for metastasis. Tumors that have metastasized may result in a guarded prognosis for your dog, contingent upon the tumor type, location, and available treatment options.

Following surgery, your dog may require an Elizabethan collar (E-collar) to prevent licking or chewing of the surgical site, which could lead to infection or stitch disruption.

Recovery duration resembles that of a routine neuter surgery, during which your dog should be kept in a calm, quiet environment with restricted activity for 10-14 days. This entails avoiding running, jumping, or rough play. If your dog is typically active, confinement to a small room or crate may be necessary to promote rest and proper healing post-surgery.

It’s essential to inspect the surgical site daily for any signs of infection such as redness, swelling, heat, discharge, or an unpleasant odor. Keeping the incision clean and dry is crucial—this means refraining from bathing or swimming until your veterinarian confirms complete healing from surgery. Your veterinarian may schedule follow-up appointments, especially if the tumor was diagnosed as cancer, to monitor for any signs of recurrence.


The most effective measure to prevent testicular tumors in male dogs is to have them assessed by a veterinarian and neutered at a young age. Depending on your veterinarian’s advice and your dog’s breed, male dogs can undergo neutering as early as two months old. For larger breeds, it might be beneficial to delay neutering until they reach full growth (typically between 9-15 months old) to reduce the risk of certain cancers and joint problems later in life.

Testicular Tumors in Dogs FAQs

Is there pain associated with testicular tumors in dogs?

While testicular tumors in dogs may not inherently cause pain, your dog may not exhibit noticeable signs of distress. However, the presence of swelling and pressure resulting from tumor growth can lead to indications of discomfort.

How prevalent are testicular tumors in dogs?

Testicular tumors rank as the most commonly occurring tumors in older, unneutered male dogs, although they can affect dogs of all breeds and ages. Fortunately, their occurrence is not widespread, as many dogs have already undergone neutering.

Scroll to Top