Testicular Tumors in Rabbits

Testicular tumors are abnormal growths that develop in one or both testicles of an intact male rabbit. Reported tumor types in rabbits include seminoma, interstitial or Leydig cell tumors, Sertoli cell tumors, and less common mixed or unusual tumors. They appear to be much less common than uterine cancer in female rabbits, but they can still cause local swelling, discomfort, and in some cases spread beyond the testicle.

Many pet parents first notice that one side of the scrotum looks larger, firmer, or misshapen. Some rabbits act normal at first, which can make the problem easy to miss. Because rabbits often hide illness, even a small change in the scrotum or groin deserves a veterinary exam.

The good news is that many localized testicular tumors are managed with surgical removal of the affected testicle, and often both testicles are removed during neuter surgery. Prognosis is often favorable when the mass is found early and there is no evidence of spread, but the outlook depends on the tumor type, how advanced it is, and your rabbit's overall health.

In most rabbits, there is no single clear cause that a pet parent could have prevented day to day. As with many cancers, risk appears to rise with age. Published rabbit case reports describe testicular tumors more often in mature to older intact males, although uncommon tumors can occur at other ages too.

Being intact is the biggest practical risk factor because a rabbit cannot develop a testicular tumor if the testicles were removed earlier in life. Some tumors may arise from germ cells, while others come from hormone-producing or supporting cells inside the testicle. In a few species, retained testicles can increase tumor risk, and a rabbit with an undescended testicle should be evaluated carefully by your vet.

This is not caused by routine handling, normal diet, or litter habits. Pet parents should not blame themselves. The most helpful step is early recognition and prompt veterinary assessment.

Diagnosis starts with a full physical exam. Your vet will compare both testicles, feel for firmness or irregular shape, and check whether the swelling seems limited to the testicle or involves nearby tissues. Because other problems can look similar, your vet may also consider abscess, trauma, hernia, orchitis, or an undescended abnormal testicle.

Common next steps include blood work to assess anesthesia readiness and overall health, plus imaging such as ultrasound or radiographs. Ultrasound can help define whether the mass is inside the testicle and whether nearby structures are involved. Chest imaging may be recommended if your vet is concerned about spread.

A definite diagnosis usually comes from histopathology after surgery. That means the removed tissue is sent to a lab to identify the exact tumor type and whether margins and surrounding structures look concerning. This information helps your vet discuss prognosis and whether monitoring alone is reasonable or whether more staging is needed.

The clearest prevention step is neutering an intact male rabbit before a testicular problem develops. Because neutering removes the testicles, it also removes the tissue where these tumors form. VCA notes that neutering eliminates the risk of testicular cancers in rabbits.

Prevention also means routine wellness exams. Rabbits are skilled at hiding pain and illness, so a subtle scrotal change may be the only early clue. Ask your vet to include a reproductive exam during regular visits, especially for intact males and senior rabbits.

At home, gently watch for asymmetry, swelling, or a new lump near the groin when handling your rabbit. Early detection matters. Finding a mass when it is still localized usually gives your vet more treatment options and may improve recovery.