Yes, rabbits can and do get cancer. Like most mammals, they develop a range of malignant and benign tumors, and cancer is one of the more common reasons older pet rabbits need veterinary care. Some cancers, particularly uterine cancer in unspayed females, are so prevalent that prevention through spaying is considered routine. Here’s what rabbit owners should know about the types, warning signs, and treatment options.
Uterine Cancer: The Most Preventable Type
Uterine adenocarcinoma is the single most common cancer in female rabbits that haven’t been spayed. The incidence is staggering: up to 80% of unspayed does develop it by age 3 to 4. Age is the strongest risk factor, and the tumor grows inside the uterus, often without obvious symptoms until it has advanced or spread to the lungs or other organs.
Early signs can include blood-tinged urine, decreased appetite, or a gradual drop in energy. Because these symptoms overlap with other conditions like urinary tract infections, uterine cancer often goes undetected until a vet performs imaging or feels an abdominal mass during an exam. Spaying a female rabbit before age 2 essentially eliminates this risk and is one of the strongest arguments for early spaying in pet rabbits.
Mammary Tumors
Mammary tumors are another significant concern for female rabbits, and the vast majority of them are malignant. Across multiple studies, carcinomas accounted for 50% to 98% of all mammary tumors examined, with adenocarcinomas being the dominant type. In one study, 119 out of 124 mammary tumors were adenocarcinomas.
Rabbits with mammary tumors frequently have concurrent uterine disease, including endometrial hyperplasia or uterine carcinoma. This overlap reinforces the value of spaying, which addresses both reproductive organs at once. If you notice lumps or swelling along your rabbit’s belly or chest, a vet visit is warranted quickly, since malignant mammary tumors can spread.
Lymphoma
Lymphoma, a cancer of the immune system’s white blood cells, is relatively common in rabbits and can appear across a wide age range. In a review of 16 cases, rabbits presented anywhere from 4.5 to 12 years old, with an average age of 8. The most common subtype is diffuse large B-cell lymphoma, the same form that predominates in humans and dogs.
The challenge with lymphoma is that its symptoms are vague. Affected rabbits typically show decreased appetite, lethargy, weight loss, and changes in behavior or fecal output. When the disease involves the digestive tract, liver, spleen, or kidneys, these nonspecific signs may be the only clue. Cutaneous (skin) lymphoma can look different: raised nodules or plaques on the skin, sometimes with crusting, redness, or hair loss. In younger rabbits under age 2, lymphoma can cause noticeable enlargement of the kidneys, spleen, liver, and lymph nodes.
Thymoma
Thymoma is a tumor of the thymus gland, located in the chest. It’s one of the more distinctive rabbit cancers because of its hallmark symptom: bilateral exophthalmos, where both eyes bulge forward. This occurs because the growing mass in the chest increases pressure on blood vessels returning from the head. In one clinical review, about 46% of rabbits with thymoma showed this eye-bulging sign.
Other common symptoms include difficulty breathing (seen in nearly 77% of cases) and exercise intolerance (about 54%). If your rabbit suddenly seems winded or reluctant to move, and especially if both eyes appear to protrude, thymoma should be on the radar. Diagnosis typically involves ultrasound-guided sampling of the chest mass. Surgical removal is possible in some cases, though outcomes vary widely.
Skin Tumors
Pet rabbits develop a variety of skin tumors, both benign and malignant. The most commonly diagnosed skin growths include trichoblastomas (a type of hair follicle tumor, generally benign), collagenous hamartomas, and lipomas (fatty lumps). These are typically slow-growing and not life-threatening, though they can become uncomfortable depending on location and size.
On the malignant side, skin cancers in rabbits include squamous cell carcinoma, fibrosarcoma, malignant melanoma, and several others like myxosarcoma and liposarcoma. Malignant melanoma was diagnosed in 8 rabbits in one large retrospective study of skin tumors. Any new lump, especially one that grows rapidly, changes color, ulcerates, or bleeds, should be evaluated. A vet can often get an initial read through a fine needle aspirate, where a small sample of cells is drawn out with a needle and examined under a microscope.
Warning Signs to Watch For
Rabbits are prey animals that instinctively hide illness, which makes cancer detection harder than in dogs or cats. Many internal tumors produce only vague signs until they’re advanced. The symptoms worth paying close attention to include:
- Loss of appetite or changes in eating habits, which can signal gastrointestinal, liver, or kidney involvement
- Weight loss that isn’t explained by a diet change
- Lethargy or reluctance to move, particularly if your rabbit was previously active
- Lumps or swellings anywhere on the body, under the skin or along the mammary chain
- Blood in the urine, which can indicate uterine or bladder tumors
- Labored breathing, a possible sign of chest tumors or lung metastasis
- Bulging eyes, the classic indicator of a thymoma or mediastinal lymphoma
- Changes in fecal production, either smaller droppings, fewer droppings, or diarrhea
- Skin changes such as new nodules, non-healing sores, crusting, or hair loss in patches
It’s worth noting that abscesses caused by bacterial infections like Pasteurella can mimic tumors. These pus-filled swellings may lurk below the skin or on internal organs for long periods before becoming apparent. A vet can distinguish between an abscess and a tumor through imaging or a tissue sample.
How Rabbit Cancer Is Diagnosed
Diagnosis follows a similar logic to cancer workups in other animals. Your vet will typically start with a physical exam and blood work, then move to X-rays or ultrasound to look for masses, organ enlargement, or fluid buildup. CT scans offer more detailed views when available, particularly for nasal or chest tumors.
A biopsy, where a tissue sample is removed and examined, is the definitive step for confirming cancer and identifying its type. Fine needle aspirates are a less invasive first step: a thin needle is inserted into a lump, cells are collected, and a pathologist evaluates them. For deeper tumors, ultrasound-guided needle biopsy allows the vet to sample tissue without major surgery. The specific tumor type matters because it determines whether surgical removal, further treatment, or palliative care is the best path forward.
Treatment and What to Expect
The most common treatment for rabbit cancer is surgical removal of the tumor, which is also the approach with the most established track record. For uterine and mammary cancers, this means spaying or removing the affected tissue. For thymoma, surgical removal is possible but technically challenging given the tumor’s location in the chest.
Radiation therapy is available at some specialized veterinary centers. In one documented case, a rabbit with an intranasal adenocarcinoma was treated with surgery followed by weekly radiation sessions over eight weeks. The rabbit remained in good condition with no tumor recurrence for more than three years afterward. While this is a single case, it illustrates that radiation can be effective in rabbits when the tumor is localized and the rabbit tolerates treatment well.
Chemotherapy is used less commonly in rabbits than in dogs or cats, partly because there’s less published data on protocols and outcomes for rabbit-specific cancers. Some exotic animal specialists do offer chemotherapy for lymphoma and other systemic cancers, but availability depends heavily on where you live and which specialists are accessible. The goal of treatment in rabbits, as in most companion animals, is generally quality of life rather than cure, particularly when cancer is caught late. Many rabbit owners work with their vet to manage pain and maintain comfort for as long as the rabbit is eating, moving, and showing interest in daily life.
The Role of Spaying and Neutering
Spaying is the single most impactful step you can take to reduce cancer risk in a female rabbit. It eliminates the risk of uterine adenocarcinoma entirely, dramatically reduces the chance of mammary tumors, and removes the hormonal environment that drives both diseases. Given that uterine cancer affects up to 80% of intact females by their mid-years, spaying is less of an elective procedure and more of a health necessity for pet rabbits expected to live into old age. Most rabbit-savvy vets recommend spaying between 4 and 6 months of age. For males, neutering removes the risk of testicular tumors, though these are far less common than uterine cancer in females.