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Cancer in Guinea Pigs: Tumours | Lymphoma + Other Cancers

Although cancer in guinea pigs is uncommon, age plays a significant role in the type of cancer they might develop. While older guinea pigs are more prone to cancer, younger ones can sometimes be diagnosed with leukaemia. In older guinea pigs, the cancers often manifest as lymphoma, mammary, skin, or uterine tumours. These cancers can be benign, which means they don’t spread, or malignant, indicating a potential to spread to other parts of the body.


Lymphosarcoma (also known as lymphoma) is a blood cancer in guinea pigs that primarily targets the lymph nodes. When a guinea pig develops this condition, one of the most telltale signs is the swelling of several lymph nodes. This swelling arises because malignant (cancerous) cells quickly invade these nodes and spread through the bloodstream. 

Symptoms of lymphosarcoma

Symptoms of lymphosarcoma can include lethargy, weight loss, difficulty breathing (known as dyspnoea), a scruffy appearance to their coat, and swollen lymph nodes. 

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Diagnosing lymphosarcoma

One of the difficulties with lymphosarcoma is that it can spread significantly before being detected. To diagnose it, vets usually first check for visible signs. If they suspect lymphosarcoma, they’ll often take a sample from the swollen lymph nodes to examine more closely.

Treatment for lymphosarcoma

The available treatments for this type of cancer in guinea pigs have limited effectiveness, and the prognosis for those diagnosed with lymphosarcoma is typically bleak, with most guinea pigs, unfortunately, succumbing to the illness just a few weeks post-diagnosis.

Two guinea pigs

Cavian leukaemia

Cavian leukaemia, a cancer specifically affecting guinea pigs, targets the blood cells and mainly affects the bone marrow. Its symptoms closely mirror those of lymphosarcoma, but a blood sample is required to diagnose cavian leukaemia accurately.

Researchers speculate that a retrovirus is responsible for its transmission. Most commonly, the transfer occurs from mother to babies. However, there are indications that transmission between unrelated guinea pigs is also possible.

Sadly, the outlook for guinea pigs diagnosed with cavian leukaemia is not good. In many cases, affected guinea pigs may only survive a few weeks post-diagnosis. 

Mammary gland tumours

Mammary gland tumours refer to cancerous growths in the glandular tissue of one or more mammary glands. These tumours can develop in both male and female guinea pigs. While they usually don’t spread, when they do, they most commonly affect the lungs and can also reach organs like the liver.

These tumours are mainly influenced by the hormones oestrogen and progesterone. They’re commonly diagnosed in guinea pigs older than three years, regardless of whether or not they’ve been neutered. 

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Symptoms of mammary gland tumours

While affected guinea pigs might maintain their usual activities, they can show altered eating or pooping habits. If the cancer spreads, especially to the lungs, they might become lethargic, depressed, experience breathing difficulties, and suffer weight loss.

The mammary glands might seem enlarged with palpable lumps. These lumps tend to be solid and painless; in some cases, there could be a brown or red discharge from the teat of the affected gland.

Diagnosing mammary gland tumours

For diagnosis, veterinarians often perform a biopsy using a fine needle to extract cells from the mass, typically without the need for general anaesthesia. Once extracted, the cells are sent to a lab for further analysis. To determine the extent of the disease, chest and abdominal x-rays are taken, though they might not always detect whether it has spread.

Treating mammary gland tumours

Surgery is usually not recommended if the cancer has spread. In such cases, palliative care focused on comfort is advised. If the cancer hasn’t spread, surgical removal of the mass and the affected glands is the standard procedure. Depending on the size and spread of the tumours, more than one surgery might be necessary. 

The prognosis is generally optimistic if it hasn’t spread. However, post-surgery, there’s always a chance of recurrence.

ginger guinea pig in hideout

Skin cancer

Skin tumours in guinea pigs can vary in type and seriousness.

  • Trichofolliculoma: This is the most common type of skin tumour in guinea pigs. It is benign (harmless) and typically presents as a firm, round nodule, often in the lower back region.
  • Fibrosarcomas: These are malignant tumours originating from fibrous connective tissue. They can be invasive and, if not addressed promptly, may spread to other parts of the body.
  • Lipomas: These are benign tumours made up of fat tissue. They are typically soft, moveable lumps beneath the skin and are not usually a cause for concern unless they grow large enough to cause discomfort or impede movement.
  • Sebaceous Adenomas: These are lumps from the sebaceous glands, which produce the oil that lubricates the skin. They are benign but can cause discomfort if they grow large or become ulcerated.
  • Pilomatrixoma: This is a rare type of harmless skin tumour that arises from hair cells. It can grow quite large and may need attention.

Sebaceous cyst are also lumps on the skin but are not cancerous. You can find out more about sebaceous cysts here…

Diagnosing skin cancer

Early detection is key to managing and treating skin cancers in guinea pigs. Regularly checking your pet for lumps, bumps, or any changes in the skin can help in early identification. 

For a definitive diagnosis, a veterinarian might perform a biopsy, where a sample of the tumour is taken for examination. This helps determine the type of tumour and the best course of action for treatment.

Treatment for skin cancer

Surgical removal remains the primary treatment for most skin tumours in guinea pigs. Depending on the type and stage of the cancer, the veterinarian might recommend additional treatments or supportive care.

three guinea pigs in a big enclosure, eating fresh leaves

Uterine cancer

The uterus is part of the female reproductive system in guinea pigs. Uterine cancer can be benign or malignant. 

Symptoms of uterine cancer

While some guinea pigs might not show any noticeable signs, common symptoms of uterine tumours can include:

  • Vaginal bleeding
  • Lethargy or reduced activity
  • Swollen abdomen
  • Changes in appetite or weight
  • Difficulty urinating

Diagnosing uterine cancer:

If a vet suspects a uterine tumour, they may conduct a physical examination and take X-rays or ultrasounds to examine the guinea pig’s internal organs. A biopsy might be performed in some cases, where a small tissue sample is taken from the uterus and examined under a microscope.

Treatment for uterine cancer

Surgical removal of the tumour or even the entire uterus (hysterectomy) is often recommended, especially if the tumour is large or causing discomfort. This can also prevent potential complications later, especially with malignant tumours that might spread.

Prognosis for uterine cancer

The outcome for a guinea pig with a uterine tumour largely depends on the type and stage of the tumour. There is often a good prognosis for guinea pigs who have had benign tumours surgically removed. However, if the tumour is malignant and has spread to other parts of the body, the prognosis may not be so optimistic.

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