Testicular Cancer in Dogs

What Testicular Cancer Is

Testicular tumors arise from the cells that make up the testicle, and they are among the most common tumors diagnosed in unneutered male dogs.

Most are found in older dogs, typically around ten years of age, though dogs with an undescended testicle can develop them considerably earlier.

Three types account for nearly all cases, in roughly similar proportions. It is common for a dog to have more than one type at once, or tumors in both testicles.

Interstitial cell tumors, also called Leydig cell tumors, are almost always benign. They very rarely spread. Many are discovered incidentally and would never have caused a problem. They can produce testosterone, which is associated with other conditions in older intact males, including perianal tumors and perineal hernias.

Seminomas arise from sperm-producing cells. The large majority behave benignly. A small proportion spread, most often in dogs with an undescended testicle.

Sertoli cell tumors are the type that most often causes complications. They are the most likely of the three to produce estrogen and the most likely to spread, though even here spread is the exception rather than the rule.

Which type your dog has is determined by sending the removed tissue to a pathologist, not by examining the testicle beforehand.

Which Dogs Are Affected

Only unneutered dogs develop testicular tumors, because the tissue they arise from has been removed in neutered dogs.

Beyond that, breeds reported more often include Boxers, German Shepherds, Weimaraners, Afghan Hounds, Shetland Sheepdogs, and Collies. Age is a strong factor — these tumors are largely a disease of older intact males.

Undescended Testicles Change the Picture

This deserves its own section because it is the single most important risk factor and because it is frequently overlooked.

A testicle that never descended into the scrotum, a condition called cryptorchidism, carries a substantially higher risk of developing a tumor than a normally descended one, with commonly cited estimates around ten times higher. Retained testicles sit either in the groin or inside the abdomen, and tumors that develop there are more likely to be Sertoli cell tumors or seminomas, the two types most associated with complications.

Retained testicles also present a second problem: you cannot feel them. A tumor growing on an abdominal testicle can reach a considerable size before anything is noticed, and it may first announce itself as an abdominal mass, as sudden severe abdominal pain from the testicle twisting on itself, or as the hormonal signs described below.

Cryptorchidism runs in families and is considered heritable, which is why affected dogs are not recommended for breeding.

If your dog has an undescended testicle, neutering removes essentially all of this risk, and both testicles should be removed. This holds true even though locating an abdominal testicle requires a more involved surgery than a routine neuter.

Signs to Look For

Many testicular tumors cause no signs at all and are found during a physical examination or discovered by the surgeon at a routine neuter.

When signs do appear, the most common are:

• One testicle noticeably larger, firmer, or a different shape than the other
• A distinct lump within a testicle
• Scrotal swelling
• The other testicle appearing to shrink
• An abdominal mass, in dogs with a retained testicle

The signs that need prompt attention

A minority of these tumors, mostly Sertoli cell tumors, produce estrogen. In dogs, sustained high estrogen suppresses the bone marrow, which is where blood cells are made. This is the mechanism by which testicular tumors occasionally become life-threatening, and it is entirely reversible in the early stages.

Hormonal signs include:

• Symmetrical hair loss on both flanks, the perineum, or the belly
• Darkening of the skin in those areas
• Enlarged nipples or mammary tissue
• A hanging or drooping prepuce
• Attracting the sexual interest of other male dogs
• Reduced interest in mating and a softening or shrinking of the unaffected testicle

Signs that the bone marrow is already affected are more urgent:

• Pale gums
• Unusual tiredness or weakness
• Bruising, or small red spots on the gums or belly
• Bleeding that seems out of proportion to a minor injury
• Fever or repeated infections

The first group warrants an appointment soon. The second group warrants one immediately. Bone marrow suppression caught early usually recovers after the tumor is removed. Caught late, it may not, and it is the main reason a dog dies of a testicular tumor.

How it is Diagnosed

Physical examination identifies most testicular tumors. Your veterinarian will palpate both testicles and check for the hormonal changes described above.

Ultrasound of the scrotum characterizes the mass. If your dog has an undescended testicle, abdominal ultrasound locates it and checks nearby lymph nodes.

Bloodwork is essential whenever hormonal signs are present, because a complete blood count reveals whether the bone marrow has been affected. This single test changes how urgently everything else proceeds.

Chest X-rays are recommended when a malignant tumor is suspected, to check for spread.

Histopathology after removal provides the definitive diagnosis. Testicles are generally not biopsied beforehand — the standard approach is to remove them and send the tissue to a pathologist, because removal is the treatment anyway. Your veterinarian will not be able to tell you with certainty which type your dog has until that report comes back, usually within a week or two.

Treatment

Neutering

Surgical removal of both testicles is the treatment, and for the great majority of dogs it is the whole treatment.

For a normally descended testicle this is a routine neuter, an operation performed in nearly every veterinary practice. For a retained testicle it is more involved — an abdominal or inguinal approach to locate and remove it — but still a well-established procedure.

Both testicles are removed even when only one appears abnormal. The remaining testicle has the same underlying risk, may already contain a tumor too small to detect, and leaving it means repeating the surgery later.

For benign tumors, which is most of them, this ends the matter permanently. The tumor is gone and it does not come back.

After the pathology report

The histopathology report tells you the type, whether the margins were complete, and whether any features suggest more aggressive behavior. For interstitial cell tumors and most seminomas, the report typically confirms that no further treatment is needed and your dog can go back to being a dog.

If the report raises concern, or if imaging showed enlarged lymph nodes or spread, your veterinarian may recommend referral to an oncologist and further staging.

The uncommon cases that need more

Spread to lymph nodes or other organs is uncommon but does occur, most often with Sertoli cell tumors and seminomas from retained testicles. Chemotherapy and radiation have been used, and seminomas in particular tend to be responsive to radiation. Evidence is limited because these cases are relatively rare, so treatment is individualized with an oncologist.

Estrogen-induced bone marrow suppression is treated first by removing the source, meaning the tumor. Beyond that, care is supportive: monitoring blood counts, antibiotics if white cells are low, and transfusions if needed. Recovery can take weeks to months, and it depends heavily on how severe the suppression was when treatment began. Mild cases usually recover fully. Severe cases carry a genuinely guarded outlook, which is why the warning signs above are worth acting on quickly.

Supportive care

For the routine case, supportive care means ordinary post-surgical care — pain medication for a few days, rest, and keeping the incision clean and undisturbed.

Nothing in the supplement or herbal category has been shown to treat testicular tumors in dogs, and none is needed for a tumor that surgery resolves completely. If your dog is in the uncommon group with spread or marrow suppression, tell your veterinarian about anything you are giving, since some supplements affect clotting and drug metabolism. Our page on integrative and supportive care covers this more fully.

What Treatment is Actually Like for Your Dog

For most dogs, considerably easier than you are expecting.

A routine neuter is a short procedure under general anaesthesia, and most dogs go home the same day. Discomfort is manageable with medication for a few days. The main challenge is usually keeping an energetic dog quieter than he wants to be for ten to fourteen days, and preventing him from licking the incision — a recovery collar or surgical suit handles this.

Surgery for a retained abdominal testicle involves an abdominal incision, so recovery is somewhat longer and activity restriction matters more, but it remains a routine operation with a straightforward recovery.

Dogs who had hormonal signs often begin improving within weeks. Hair regrows, skin colour normalizes, and enlarged mammary tissue recedes, though full resolution can take several months.

There is no chemotherapy for the overwhelming majority of these dogs, no repeat visits beyond a suture check, and no ongoing treatment.

Understanding the Outlook

For most dogs with a testicular tumor, the outlook is excellent and life expectancy is unaffected.

Benign tumors removed by neutering are gone permanently and do not return. Malignant tumors that have not spread are, in most cases, also resolved completely by removal. Because spread is uncommon, the majority of dogs diagnosed with testicular cancer go on to die of something entirely unrelated, years later.

The outlook is less certain in two situations. Tumors that have already spread to lymph nodes or distant organs at the time of diagnosis carry a more guarded prognosis, and treatment is individualized. Severe bone marrow suppression from estrogen carries a guarded outlook that depends on how much marrow function remains and whether it recovers.

Both of these are the exception. If your dog has a firm testicle and no other signs, the likely path is one surgery and a full recovery.

What It Costs

Costs vary widely by region and practice type. Ask for a written estimate.

• Examination and scrotal ultrasound: approximately $300 to $700
• Routine neuter: approximately $200 to $800, with low-cost clinics available in many areas
• Surgery for a retained abdominal testicle: approximately $500 to $1,500
• Histopathology: approximately $150 to $400
• Staging, if malignancy is suspected: approximately $500 to $1,500
• Treatment for severe bone marrow suppression: potentially several thousand dollars, involving hospitalization and transfusions

This is, financially as well as medically, among the most manageable cancer diagnoses on this site. Do not skip the histopathology to save money — it is the step that tells you whether anything further is needed.

After Surgery

Restrict activity for ten to fourteen days, keep the incision dry, and prevent licking. Watch for swelling, discharge, or an incision that opens, and call your veterinary practice if you see any of these.

Ask for the pathology report and keep a copy. If it confirms a benign tumor with complete removal, no further monitoring is usually required beyond your dog's normal check-ups.

If the report indicates a malignant tumor, your veterinarian will advise on a recheck schedule, typically including periodic physical examinations and chest X-rays.

Dogs who had hormonal signs should have their blood counts rechecked until they normalize.

A Note on Prevention

Neutering prevents testicular cancer completely, because it removes the tissue the tumor forms in. That makes this one of the very few cancers that is essentially entirely preventable, and it is the main reason testicular tumors are seen far less often now than they once were.

If you are reading this because your dog has already been diagnosed, this is not a reproach. Testicular tumors are usually benign, plenty of well-cared-for dogs are left intact for perfectly sound reasons, and the outcome for your dog is likely to be good regardless.

The timing question is genuinely more complicated than it once appeared. Neutering eliminates testicular tumor risk and reduces some other conditions, but research in certain large breeds has associated early neutering with increased risk of some other cancers and joint disorders. The evidence varies by breed and is still developing. This is a real conversation to have with your veterinarian about your specific dog rather than a question with one universal answer.

Questions Worth Asking Your Veterinarian

• Can you feel both testicles, and is either one abnormal?
• Does my dog have any signs of hormonal changes?
• Should we run bloodwork before surgery?
• Will you send the tissue for histopathology, and when will results come back?
• If my dog has a retained testicle, what does that surgery involve?
• Does anything on the pathology report suggest we need further tests?
• What should I watch for during recovery?

Common Questions

Is testicular cancer in dogs usually serious? Usually not. The majority of testicular tumors in dogs are benign or behave benignly, and neutering resolves them completely. The two situations that are serious: spread to other organs, and estrogen-induced bone marrow suppression, are both uncommon.

Does neutering get rid of it completely? For benign tumors, yes. Removing both testicles removes the tumor entirely, and it does not come back. The same is true for most malignant tumors that have not yet spread.

Why does the healthy testicle have to come out too? Because it carries the same underlying risk, may already contain a tumor too small to feel, and leaving it means facing a second surgery later. Removing both at once is standard practice.

My dog is losing hair and his nipples look enlarged. Is that related? It can be. Those are signs of a tumor producing estrogen, most often a Sertoli cell tumor. It warrants an appointment soon, including bloodwork, because sustained high estrogen can suppress the bone marrow. Most dogs recover fully once the tumor is removed.

My dog has an undescended testicle but seems fine. Does it need to come out? Yes. A retained testicle carries a substantially higher tumor risk, cannot be monitored by touch, and can twist painfully. Removing it is the standard recommendation even in a dog with no current signs.

Is my dog too old for surgery? Age itself is rarely the deciding factor. Pre-anesthetic bloodwork and an examination assess whether your specific dog is a reasonable candidate, and many older dogs come through routine neuters without difficulty. Discuss the specifics with your veterinarian rather than assuming.

Could this have spread already? It is possible but not likely. Spread occurs in a minority of cases, most often with Sertoli cell tumors and seminomas arising in retained testicles. Chest X-rays and an examination of the lymph nodes will answer this for your dog.

This page is for education and does not replace advice from your own veterinarian, who knows your dog. If your dog has an enlarged testicle, an undescended testicle, or any of the hormonal signs described above, book an appointment with your veterinary practice.