Testicular Tumours in Dogs: Lumps, Hormonal Signs and Treatment
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By Dr Duncan Houston
A new lump or change in the size of a dog's testicle deserves a veterinary examination, even when it seems painless. Some tumours remain localised, while others cause important hormonal effects before a dog appears generally unwell.
Dogs with a retained testicle need particular attention because the affected tissue may be inside the abdomen or groin rather than visible in the scrotum.
Quick Answer
Testicular tumours occur mainly in intact male dogs, especially older dogs and those with undescended testicles. A new lump, asymmetry, unexplained hair loss or enlarged mammary tissue warrants prompt assessment. Surgery often provides effective treatment for localised disease, but sudden pain, collapse, pale gums or abnormal bleeding needs urgent care.
The main tumour types
The three common categories arise from different cells within the testicle. More than one type can be present in the same dog, and appearance alone cannot reliably identify them.
| Type | Important features |
|---|---|
| Interstitial, or Leydig cell tumour | Often small and localised; hormonal activity can occur, so a quiet-looking lump still needs assessment |
| Seminoma | Arises from sperm-producing germ cells; many remain localised, but spread is possible |
| Sertoli cell tumour | Can produce excess oestrogen, with effects on skin, reproductive tissues and sometimes bone marrow |
A recent review of canine testicular-tumour management emphasises that hormonal effects can matter as much as malignant behaviour. A reassuring size or slow growth rate is not enough to choose observation without further assessment.
Why an undescended testicle changes the risk
Cryptorchidism means one or both testicles have not descended into the scrotum. A retained testicle may be in the groin or abdomen. A dog with one normal descended testicle can still be fertile.
Retained testes carry increased tumour risk and can twist on their blood supply, causing acute pain. Your vet should confirm whether a missing testicle was surgically removed or is retained; the scrotum alone cannot answer that question.
The American College of Veterinary Surgeons discusses castration for retained testes and testicular disease. Removal of both testes is generally recommended in cryptorchid dogs, and affected dogs should not be bred. The operation may require a groin or abdominal approach.
Signs you may notice
- A new lump, firmness or unequal testicle size.
- Enlargement or discomfort of the scrotum.
- Persistent licking around the genital area.
- Symmetrical hair loss or darkened skin.
- Enlarged nipples or mammary tissue.
- Reduced fertility or changes noticed during a breeding examination.
Some dogs have no obvious signs and the problem is found at a routine visit. A mass in a retained testicle can enlarge without producing an obvious external lump.
Excess oestrogen can suppress blood-cell production in the bone marrow. The Merck Veterinary Manual describes this hormone-associated complication. Anaemia, infection risk and abnormal bleeding can become life-threatening, so skin changes accompanied by weakness should not be treated as merely cosmetic.
When is it urgent?
| Finding | Action |
|---|---|
| Sudden severe scrotal or abdominal pain, repeated vomiting or collapse | Emergency assessment now; torsion and other acute problems need exclusion |
| Pale gums, pronounced weakness, unexplained bruises or bleeding | Urgent same-day care, immediately if the dog is unstable |
| Hot painful swelling, discharge or fever | Prompt same-day assessment for infection or inflammation |
| A painless new lump or gradual asymmetry in an otherwise well dog | Arrange an appointment soon rather than waiting for the next annual visit |
Do not squeeze, repeatedly manipulate or attempt to drain a swelling. Prevent persistent licking while arranging care and avoid giving human painkillers.
A lump is not always a tumour
Other explanations include inflammation of the testicle or epididymis, trauma, torsion, a scrotal skin lesion or a hernia. Some infections have implications for breeding contacts and people, so give your vet a complete reproductive and travel history.
Squatting to urinate alone is not evidence of a hormone-producing tumour. Changes in urination may instead involve discomfort, urinary disease, prostate disease or ordinary behaviour.
How your vet investigates
The examination includes both testes when present, the scrotum, groin and relevant surrounding tissues. Ultrasound can help locate retained tissue and assess a mass.
Blood testing is particularly important if hormonal effects or general illness are suspected. Urine tests and assessment for infection may be appropriate. Imaging of the abdomen, chest or lymph nodes is selected according to concerns about spread and the patient's overall condition.
Microscopic examination of removed tissue, called histopathology, usually establishes the tumour type and helps guide follow-up. Ask when the pathology result will be available and whether it changes the treatment plan.
Treatment and realistic expectations
Surgical removal is the main treatment for most testicular tumours. Your vet will discuss whether both testes should be removed and how any retained tissue will be approached. Overall health, tumour findings and reproductive considerations affect planning.
Many localised tumours have a favourable outlook after surgery. If spread is found, an oncology consultation may be appropriate. Severe bone-marrow suppression can require intensive support, and removing the hormone source does not guarantee immediate marrow recovery.
Age alone does not determine whether surgery is reasonable. Pre-anaesthetic assessment helps weigh the dog's actual health and the consequences of leaving the disease untreated. Monitoring without surgery is an individual decision, not a default because a lump looks benign.
Recovery and prevention
Follow the surgeon's activity restriction and recheck instructions. Prevent licking with a properly fitted protective collar, give prescribed pain relief and inspect the incision daily. Report increasing swelling, discharge, opening of the wound, persistent appetite loss or worsening discomfort.
Abdominal surgery for a retained testicle may require a different recovery plan from a straightforward scrotal procedure. Do not use a fixed calendar date as permission for running if healing has not been checked.
Removing testicular tissue prevents tumours arising in that tissue. Timing of elective neutering should be discussed individually; UC Davis describes the broader health considerations that influence this decision. A retained testicle is a distinct medical concern.
Common mistakes
- Assuming a painless lump cannot be important.
- Ignoring hormonal skin changes because the testes look normal externally.
- Using tumour percentages from one study as an individual prognosis.
- Waiting indefinitely for an adult dog's retained testicle to descend.
- Skipping pathology or the postoperative review.
Frequently asked questions
Does a testicular tumour always mean aggressive cancer?
No. Many remain localised, but tumour type, hormone production and staging determine the risk.
Can a neutered dog develop one?
A dog with both testes completely removed cannot develop a tumour in those removed organs. A scrotal or groin lump still needs examination, particularly if surgical history is uncertain.
Will hair grow back after treatment?
Hormone-related coat changes may improve after the source is removed, but timing varies and other skin disease may coexist.
Can I just monitor the size at home?
Home observations are useful between visits, but they cannot identify tumour type, hormonal effects or internal spread.
A prompt assessment can distinguish a local surgical problem from a condition needing more extensive care. The aim is to treat the whole dog, not simply the visible lump.
ASK A VET™ can help you understand the questions to ask about a testicular lump, pathology result or recovery plan.
