By Dr Duncan Houston
A change in a dog’s testicle can be easy to overlook, particularly if the dog is eating and behaving normally. Some testicular tumours cause few outward signs, while others produce hormones that affect the whole body.
Finding a lump does not automatically mean aggressive cancer. It does mean an examination is needed to identify what is happening and plan treatment.
Quick Answer
Testicular tumours occur mainly in unneutered male dogs, with increased risk when a testicle is retained in the groin or abdomen. Many remain localised and can be successfully treated by surgical removal, but hormone effects and spread can complicate the outlook. Arrange an examination for any new swelling; sudden severe pain, collapse or pale gums requires urgent care.
Which tumours occur?
The three common groups are Sertoli cell tumours, seminomas and interstitial, or Leydig cell, tumours. Their behaviour differs, and more than one type may be present. The term tumour describes abnormal growth; it does not by itself establish malignancy.
Veterinary information on testicular tumours describes their generally low rate of spread and the importance of examining removed tissue. Appearance or size alone cannot reliably identify the tumour type.
Why is a retained testicle important?
In cryptorchid dogs, one or both testicles have not reached the scrotum. A retained testicle can develop a tumour that is hidden from an external check. It can also twist on its supporting cord, causing painful loss of blood supply.
If you can only see or feel one testicle and do not have a clear surgical history, ask the vet to establish where the other is. Do not assume it was removed or that an apparently empty scrotum proves a dog has been fully neutered.
Signs you may notice
Possible local changes include a new lump, firmness, unequal testicle size, scrotal swelling or repeated licking. Some tumours are discovered incidentally during an examination.
Sertoli cell tumours can release oestrogen, causing symmetrical hair loss, darkened skin or enlarged mammary glands. Excess oestrogen may also suppress bone-marrow production of blood cells, leading to weakness, infection risk or bleeding. These effects can be serious even when a tumour has not spread.
How urgent is the change?
| What you notice | Main concern | Action |
|---|---|---|
| Painless new lump or asymmetry, dog otherwise well | Tumour or another local change | Book a prompt examination. |
| Hair loss with mammary enlargement in an intact male | Possible hormone-producing tumour | Arrange veterinary assessment and blood testing promptly. |
| Sudden painful swelling, vomiting or abdominal pain | Torsion, trauma or another acute problem | Seek urgent care now. |
| Pale gums, collapse, unexplained bruising or bleeding | Anaemia, blood-cell abnormality or internal illness | Go to an emergency service. |
What else could cause swelling?
Inflammation or infection of the testicle and nearby structures, trauma, fluid accumulation, a cyst, skin disease or a hernia can resemble a tumour. A painful area may be difficult to examine safely at home.
Prevent licking if a protective collar can be fitted comfortably. Do not squeeze a lump, puncture swelling or apply creams in an attempt to test what it is. Photographs showing a change over time can supplement the examination, but should not delay it.
How does the vet investigate?
The assessment starts with both testicles, the abdomen and the full medical history. Depending on findings, blood counts, blood chemistry, urine tests and ultrasound may be needed. Blood counts are particularly important when hormone effects or general illness are suspected.
Imaging and sampling of suspicious lymph nodes can help check for spread. Removed tissue is generally submitted for histopathology, which identifies the growth microscopically and helps guide follow-up. Ask when the result will be available and who will discuss it with you.
Treatment and recovery
Surgical removal of the testicles is the main treatment. A retained abdominal testicle requires a different surgical approach from a routine scrotal procedure. The anaesthetic and recovery plan should reflect the dog’s overall health, tumour location and any blood-cell abnormalities.
BluePearl’s specialist overview notes that surgery cures many localised cases, while severe bone-marrow damage can remain dangerous despite removal. Dogs with spread may need oncology assessment to discuss additional treatment and realistic goals.
At home, follow the surgeon’s activity and wound instructions, prevent licking and give only prescribed medication. Increasing swelling, bleeding, wound discharge, poor appetite or marked lethargy should be reported. Recovery is assessed by the dog’s progress, not a guaranteed number of days.
Your next steps
- Book an examination for any new testicular change.
- Bring neutering records, medication details and a timeline of signs.
- Ask whether hormone effects, retained tissue or spread need investigation.
- Confirm the pathology and follow-up plan before discharge.
- Keep emergency contact details available during recovery.
Common mistakes
- Waiting because the lump does not hurt.
- Assuming all testicular tumours behave the same way.
- Believing removal instantly resolves every hormone complication.
- Skipping pathology because the swelling has been removed.
Prevention and ongoing care
Complete surgical castration removes the tissue in which these primary tumours develop. Discuss the timing and wider benefits and risks individually with your vet. A retained testicle deserves a specific management plan, and cryptorchid dogs should not be bred. Neutering does not prevent every other cancer or prostate condition.
Frequently Asked Questions
Is every testicular lump cancer?
No. Several other conditions can cause swelling, and tumours differ in behaviour.
Can a dog with one visible testicle still have a tumour?
Yes. A retained testicle may be hidden in the groin or abdomen.
Is surgery always curative?
Many localised tumours have a good outcome, but spread and severe hormone complications change the outlook.
Should sudden testicular pain wait for a routine appointment?
No. Seek urgent assessment, particularly with vomiting or abdominal pain.
Early assessment keeps the options clear
A prompt examination can distinguish a manageable local problem from a condition affecting the whole dog. Treatment decisions should follow the findings and your dog’s comfort.
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