Testicular Tumours in Dogs: Signs, Treatment and When to Act

By Dr Duncan Houston

A new lump or change in testicle size is worth checking even when your dog seems comfortable. Many testicular tumours remain localised and can be treated successfully, but appearance alone cannot show the tumour type.

A testicle retained inside the abdomen can also develop disease, so an apparently empty scrotum does not always mean a dog has been fully castrated.

Quick Answer

Testicular tumours occur mainly in entire male dogs, with increased concern in dogs with retained testicles. Signs include enlargement, asymmetry, lumps and sometimes hormone-related hair loss or mammary development. Book a prompt examination for any change; sudden severe abdominal or scrotal pain, collapse, pale gums or unexplained bleeding require emergency care.

What types occur?

The main types are Leydig cell tumours, seminomas and Sertoli cell tumours. A dog may have more than one tumour type. Many do not spread, but some produce hormones or behave aggressively; laboratory examination of removed tissue helps establish the diagnosis.

Sertoli cell tumours can produce excess oestrogen, causing symmetrical hair loss, skin changes or enlarged mammary glands. Severe hormone effects can suppress bone marrow, affecting red cells, white cells and platelets. These complications can be serious even if the tumour itself has not spread.

Why do retained testicles matter?

Cryptorchidism means one or both testicles have not reached the scrotum. The Cornell canine health resource explains the associated cancer and torsion risks. A retained testicle can twist on its blood supply and cause sudden pain. Affected dogs should not be bred, and removal of retained tissue should be discussed with the vet.

How urgent is a change?

What else could cause swelling?

Infection or inflammation of the testicle or epididymis, trauma, a scrotal skin problem, fluid accumulation or a hernia can look similar. Acute pain raises concern for torsion as well as infection. The vet may consider infectious causes and breeding history when assessing inflammation; do not squeeze or repeatedly manipulate the area.

How do vets diagnose and treat it?

An examination checks both testicles, the scrotum, abdomen and regional lymph nodes. Ultrasound can locate retained tissue or characterise an abnormality. Blood tests are particularly important when hormone effects or systemic illness are suspected. Chest or abdominal imaging and sampling of concerning lymph nodes may be advised to assess spread.

Surgery to remove affected testicular tissue is the main treatment, commonly as castration. Removal of scrotal skin is not automatically required. Histopathology confirms tumour type and informs follow-up. Dogs with spread or severe bone-marrow effects may need specialist treatment and have a more guarded outlook.

What should you do at home?

1. Note when the change began and any effects on appetite, energy, coat or urination.
2. Prevent licking if it is injuring the skin and arrange the appropriate appointment.
3. Do not give human pain medicines or apply creams without advice.
4. After surgery, follow the specific rest, wound protection and medication plan, and attend the recheck to discuss the laboratory result.

Common mistakes and prevention

• Assuming painless means harmless.
• Believing one visible testicle proves the other was removed.
• Skipping tissue analysis because the lump looked benign.
• Using one fixed neutering age for every dog without considering individual needs.

Complete removal of testicular tissue prevents future tumours arising in that tissue. Discuss castration timing with your vet, especially for cryptorchid dogs. Entire males need testicular assessment during routine examinations.

Frequently asked questions

Does an enlarged testicle always mean cancer?

No. Inflammation, injury and other problems can look similar, so examination is needed.

Can surgery cure a testicular tumour?

Often, when disease is localised. Tumour type, spread and hormone-related complications determine the outlook.

Can a castrated dog develop a testicular tumour?

Not if all testicular tissue was removed. A new scrotal lump still needs assessment for other causes or retained tissue.

Further reading

See Clinical Management of Testicular Tumors in Dogs and the MSD Veterinary Manual on testicular inflammation.

The useful next step is a diagnosis, not guessing whether a lump is benign. Earlier assessment gives you a clearer treatment plan.

ASK A VET™ provides practical information to help you understand your dog's care. Sudden pain, weakness or bleeding needs urgent veterinary attention.