Testicular Tumors In Dogs

What Every Owner Should Know

A practical guide to spotting the signs, understanding diagnosis, and supporting your dog through treatment and recovery.

What Are Testicular Tumors/Cancer?

Testicular tumors are growths that develop in one or both of a male dog’s testicles. They are actually among the most common tumors found in intact (unneutered) male dogs, especially as dogs get older. The good news is that most of these tumors are not aggressive, and many dogs do very well once the affected testicle is removed.

There are three main types that vets typically see. Sertoli cell tumors come from the cells that support sperm development. Seminomas arise from the cells that actually produce sperm. Interstitial cell tumors (also called Leydig cell tumors) come from the cells responsible for testosterone production. Some dogs develop more than one type at the same time, which is part of why a thorough exam matters.

Which Dogs Are at Risk?

The single biggest risk factor is being intact (hasn’t been neutered where both testicles are surgically removed). If your dog has not been neutered, his testicles continue producing hormones throughout his life, and over time that constant hormonal activity raises the odds of a tumor forming. Age also plays a big role, since most cases show up in dogs that are middle aged or older.

One condition that significantly raises risk is cryptorchidism, which is when one or both testicles fail to descend into the scrotum and instead stay tucked up in the abdomen or groin area. A retained testicle is far more likely to become cancerous than one that descended normally, sometimes by a factor of many times over. Breeds that are more prone to cryptorchidism, such as Yorkshire Terriers, Pomeranians, Toy Poodles, and Boxers, tend to show up more often in tumor statistics as a result.

Signs and Symptoms to Watch For

Testicular tumors can be sneaky. Many grow slowly and don’t cause obvious pain, so they sometimes go unnoticed until they’ve gotten fairly large. Here are some things to keep an eye on:

A testicle that looks larger, smaller, firmer, or different in shape compared to the other one
A lump or swelling you can feel on or around the scrotum
Swelling in the abdomen, if the affected testicle never descended
Hair loss, thinning coat, or skin changes around the flanks and belly
Enlarged mammary glands or a sagging, feminized appearance in a male dog
A drooping prepuce, attraction from other male dogs, or a noticeable change in behavior or temperament

Those last few signs are linked to a syndrome some Sertoli cell tumors cause by producing excess estrogen. This can also suppress the bone marrow, which is a serious complication, so any of those hormonal changes are worth a prompt vet visit rather than a wait and see approach.

How Vets Diagnose Testicular Tumors

Diagnosis usually starts with a physical exam, where your vet will feel both testicles for size, texture, and any irregularities. If a retained testicle is suspected, an abdominal ultrasound can help locate it and check for masses. Blood work is often recommended too, both to look at overall health and to check for signs of the bone marrow problems mentioned above.

Chest X-rays or abdominal imaging may be used to check whether a tumor has spread, although this is uncommon with most testicular tumors. In many cases, the definitive answer comes after surgery, when the removed tissue is sent to a lab for a biopsy that confirms the tumor type.

Treatment Options

Neutering (Castration)

Surgical removal of both testicles is the standard treatment, and for most dogs it’s also the cure. Even if only one testicle has a tumor, vets generally remove both to eliminate the risk of a tumor developing on the other side later. If a retained testicle is involved, the surgery is a bit more involved since the vet needs to locate and remove tissue from inside the abdomen, but it’s still a routine procedure for an experienced surgeon.

Additional Treatment for Spread

Most testicular tumors are caught before they spread, but in the rare cases where a tumor has metastasized, your vet may discuss chemotherapy or other follow up treatments. This is more often a concern with seminomas in dogs that have a retained testicle, so your vet will tailor the plan based on the specific tumor type and your dog’s overall health.

Managing Hormonal Complications

If your dog has developed bone marrow suppression from a hormone producing tumor, your vet may recommend supportive care alongside surgery, which can include monitoring blood counts closely and, in some cases, hospitalization until the levels stabilize. The good news is that once the tumor is removed, hormone levels typically return to normal and related symptoms often improve over the following weeks to months.

Recovery and Outlook

The outlook for most dogs with testicular tumors is genuinely good. The majority of these tumors, even when fairly large, do not spread, and removing the affected tissue is often all that’s needed. Recovery from neutering surgery typically takes about ten to fourteen days, during which your dog may need to wear a recovery collar to prevent licking the incision or chewing the sutures out, or a onesie, also avoid running and jumping, and have the incision checked regularly for swelling, redness, or discharge. If the pet is too active a seroma can develop in the scrotum which will cause it to swell with fluid.

For dogs that had a more complicated case, such as a retained testicle or hormonal symptoms, your vet may want follow up bloodwork to confirm everything has returned to normal. Most dogs go on to live completely normal lives afterward, with no lasting effects beyond the obvious one.

The Case for Early Neutering

Because testicular tumors are tied so closely to having intact testicles, neutering your dog at an age recommended by your vet essentially removes this risk altogether. This is especially important for dogs with a retained testicle, since that tissue carries a much higher cancer risk and is also harder to monitor at home because you can’t feel or see it.

If you’ve chosen to keep your dog intact for breeding or other reasons, regular vet checkups become even more important. Routine exams give your vet a chance to catch any changes early, well before they become noticeable to you at home.

When to Call Your Vet

You don’t need to panic over every small change, but it’s worth scheduling a visit if you notice any of the following:

Any new lump, swelling, or asymmetry involving the testicles or scrotum
Unexplained hair loss, skin changes, or weight shifts
Changes in behavior, energy level, or interest from other dogs
A male dog that was never confirmed to have two descended testicles as a puppy

Catching a testicular tumor early almost always means a simpler treatment and a smoother recovery, so when in doubt, it’s always worth getting your dog checked out.