No-one wants to hear that their special friend might have cancer, but unfortunately rabbits can be affected by different forms of cancer. Some are more common than others. Our expert vets at Vetstream have put together the following information so you can understand the signs, symptoms and treatment of rabbit cancer.

What is Cancer?

Cancer is the term used for diseases where abnormal cells divide uncontrollably. These abnormal cells can form lumps or masses called tumours. Tumours can interfere with the normal function of the organs they affect, or release substances like hormones that alter the way the body functions. These abnormal cells can also invade other tissues.

In affected rabbits, cancer cells can spread from the original site of the cancer through the bloodstream and lymphatic system to other parts of the body (metastasise). When this metastatic spread happens, the cells destroy other healthy tissues in a process called metastasis.

Signs of cancer are different depending on which part of the body is affected, if and where it has spread, and how advanced it is.

Can Rabbits get Cancer?

Yes, unfortunately rabbits can get cancer! The main types are adenoma, carcinoma, sarcoma, leukaemia, lymphoma and myeloma, and central nervous system cancers. Adenomas usually occur in glandular tissues. Carcinomas are usually found in skin or tissues that line or cover internal organs.

Sarcomas are found in bone, cartilage, fat, muscle, blood vessels and other connective or supportive tissues. Leukaemias are cancers of blood-forming tissue like bone marrow. Lymphoma and myeloma affect the white blood cells of the immune system. Central nervous system cancers are found in the brain and spinal cord.

Common cancers affecting female rabbits include uterine adenocarcinoma, and mammary adenocarcinomas. In male rabbits, testicular neoplasia is the most common cancer, but it’s actually relatively rare in pet rabbits.

How Does Uterine Cancer (Adenocarcinoma) Affect Rabbits ?

This is the most common tumour seen in female rabbits. It’s reported to affect up to 80% of unspayed female rabbits before five years of age. Some breeds, including Dutch, Dwarf lop, English and Netherland Dwarf rabbits appear to be more prone to this type of cancer, but it can affect any breed.

Signs of uterine cancer may include reproductive failure like abortion or stillborn kits. In the later stages of the disease, does may become anorexic, depressed, lethargic and lose weight. You may see blood in the urine and bloody discharge from the vagina. Advanced cases of uterine cancer may have secondary tumours in the lungs which can lead to problems breathing.

Because it’s a slow growing tumour, it can be a prolonged disease, lasting months or even years. Owners often don’t notice anything is wrong until the disease has reached an advanced stage. If the cancer has spread to other organs, treatment often isn’t possible, meaning euthanasia is the kindest option. But, if caught early, spaying your rabbit to remove all the cancerous tissue is a treatment option.

What is Lymphoma / Lymphosarcoma in Rabbits?

This is cancer of the lymphatic system. It can affect the lymph nodes, spleen, liver, bone marrow, gastrointestinal tract, eyes and skin. It’s commonly seen in young rabbits and is the second most common cancer in rabbits. Signs of disease include raised nodules on the skin, hair loss, lethargy, weight loss, fever, diarrhoea, and much more!

 Mammary Carcinoma / Adenocarcinoma in Rabbits

These are tumours of the glandular tissue of the mammary glands (teats). They’re common in adult female rabbits that haven’t been spayed. Some mammary cancers remain benign (don’t spread) but others can metastasise to other parts of the body.

This cancer most commonly spreads to the lungs but can spread to other organs too. This type of cancer can affect any breed, but Belgian Hares and English breeds seem to be more commonly affected.

Signs can include irregular-sized nipples, swelling around the teats, abnormal discharge from the nipples, and open wounds. These tumours aren’t normally painful, although secondary infection can sometimes be a problem.

Types and Symptoms of Testicular Cancer in Male Rabbits

Testicular cancer has been reported in rabbits, but it’s quite rare. There are four types, seminomas, Sertoli cell tumours, interstitial cell tumours and teratomas. Interstitial cell tumours are the most common type of tumour found in male rabbits.

It’s usually seen in older rabbits and there aren’t often any signs. But signs of disease can include testicle enlargement. Testicular cancer can spread to other organs, especially the lungs, with noticeable breathing problems.

How Will My Vet Diagnose Cancer in My Rabbit?

Your vet will examine your rabbit for any lumps and bumps. Clinical signs vary depending on the type and location of the cancer, so it can be tricky to diagnose. Uterine adenocarcinomas are often diagnosed by feeling a lump in the area of the uterus (womb).

They can then take x-rays or ultrasound images to see exactly where the tumour is. Other imaging techniques like computed tomography and magnetic resonance imaging can also be performed but aren’t often used because they’re very expensive!

Diagnosis of mammary carcinomas and adenocarcinomas can be made by taking a biopsy (tissue sample) from the tumour by inserting a needle and collecting some of the cells (fine needle aspiration). Your vet will then look at the cells under a microscope. Confirmation of a cancer diagnosis will then be made by surgically removing the tumour and sending samples to a laboratory to perform an in-depth study of the tissues and cells under a microscope (histopathological examination).

Is Rabbit Cancer Treatment an Option?

Most cancers can be treated with surgery if caught in time. A full clinical examination will need to be completed by your vet, including x-ray, to make sure the cancer hasn’t spread before treatment can begin. If surgery is an option, once the tumours have been removed, x-rays will be needed every 3-6 months after surgery to make sure the cancer hasn't spread.

Getting female rabbits spayed at an early age to prevent uterine cancer from developing is essential. If your rabbit already has uterine cancer, spaying is usually the best treatment option, providing secondary tumours aren’t present.

If the cancer has spread, unfortunately prognosis is very poor. Chemotherapy isn’t usually successful for rabbits. In advanced cancer cases, the kindest thing is to have your rabbit euthanised, so they don’t have to go through any unnecessary pain or suffering.

If your rabbit has a mammary carcinoma or adenocarcinoma, partial or complete mastectomy (where the mammary gland tissue is surgically removed) and spaying is the best treatment. Tumours that haven’t spread may not need treatment but are usually removed because they can grow quite big. Tumours that spread into the bone marrow, lungs or lymph nodes, carry a very poor prognosis. Surgical removal won’t cure these cases.

For testicular tumours, castration is the treatment of choice and the only way to prevent the disease. Again, if they haven’t spread to other parts of the body, then castration should be curative. But if it has spread to the lungs, treatment is often ineffective. In these cases, euthanasia is the best option.

What Other Types of Cancers Affect Rabbits?

Rabbits can also get papillomas, basal cell carcinoma, osteosarcoma, lymphoma and thymoma.

Papillomas are wart-like growths that can develop on the skin and in the mouth. They have a cauliflower-like appearance and can bleed if your rabbit scratches them. Luckily, they tend not to spread to other parts of the body. Papillomas that develop in the mouth are considered “non-cancerous”.

Basal cell carcinoma is another type of skin cancer. It can be benign or malignant and looks like a red patch on the skin. It grows slowly and will appear over time. Although it can spread locally, they rarely spread to other parts of the body.

Osteosarcoma affects the bone but luckily is quite rare in rabbits. Signs of osteosarcoma may include lameness and hard swellings on the legs.

Thymomas are also rare tumours. The only sign of a problem may be bulging eyes. A thymoma may, in fact, be slowly growing in the chest, compressing the vessels that transport blood to the head resulting in the eyes protruding.

The most common cancers in rabbits are those affecting the reproductive system. Having your rabbit neutered at a young age to remove the uterus and ovaries or testes is the best way to eliminate the chance. It’s possible for your rabbit to suffer from other types of cancer, but treatments are always advancing, and your vet will discuss the best treatment options with you. 

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Content provided from Vetstream's Vetlexicon Lapis – www.vetlexicon.com/treat/lapis

Vetlexicon is the world’s largest peer-reviewed online clinical reference source. All our content is written and peer-reviewed by over 1,000 of the world’s leading veterinarians, ensuring relevance, accuracy and quality.