Tumors and Cancers in Guinea Pigs

What are Tumors and Cancers in Guinea Pigs?

A tumor is a mass of abnormal cells forming new tissue or growth. Tumors may be benign, or non-cancerous, or they may be malignant, or cancerous.

A benign tumor usually grows slowly and does not invade surrounding tissue or spread to other parts of the body. Malignant tumors, however, can invade surrounding lymph nodes or even spread (metastasize) to distant parts of the body.

Tumors in guinea pigs are relatively uncommon, but they have been seen in pigs as young as four months. It is more common for tumors to appear after age three. Among older guinea pigs, it’s estimated about 30% will develop tumors.

The most common sites for tumors in guinea pigs include their lungs, skin, mammary glands, ovaries, uterus, and blood/lymphatic systems. Intestinal, bladder, bone, muscle, adrenal gland, and liver tumors are rare.

Symptoms of Tumors and Cancers in Guinea Pigs

The symptoms associated with any tumor depend on where it occurs, including:

• Reproductive tumors (uterus, ovaries) can cause a distended belly, abdominal pain, and bloody vaginal discharge.

• Skin tumors usually occur on the rump but can happen anywhere. Firm, round nodules can become ulcerated and produce a discharge.

• Mammary gland tumors may cause swelling of one or more glands with clear or bloody discharge.

• Lung tumors may cause similar signs of pneumonia: trouble breathing, sneezing, coughing, lethargy, and anorexia.

• Lymphocytic leukemia is often accompanied by anorexia, lethargy, poor hair coat, and enlarged lymph nodes.

• T-cell lymphoma may cause itchiness, fur loss, crusts on the skin, enlarged lymph nodes, and changes to the surface of the eye.

Causes of Tumors and Cancers in Guinea Pigs

Like all animals, the longer guinea pigs live, the higher chance that tumors can occur. Tumor occurrence likely involves genetics and environmental components, but it is not completely understood why guinea pigs develop tumors.

The most common tumor in guinea pigs is a benign lung tumor called a bronchogenic papillary adenoma. These tumors represent 30-35% of all tumors in guinea pigs over age three. They are benign and grow slowly but can take up so much lung space that it mimics signs of pneumonia. They typically do not respond to therapy.

The second most common type of tumor is a benign skin tumor. These represent about 15% of all tumors in guinea pigs. The most common type is a trichofolliculoma, which occurs primarily in males and is benign. They can be removed with surgery.

Mammary gland tumors are also relatively common and may be more common in males. Typically, they are benign fibroadenomas, but some researchers estimate that between 30-75% of mammary tumors are a malignant type called fibro adenocarcinoma. These can invade local tissue and can metastasize to the lungs.

Benign uterine and ovarian tumors are relatively common in female guinea pigs that have not been spayed. Uterine tumors are often leiomyomas, and ovarian tumors are often teratomas.

Lymphocytic leukemias are more common in guinea pigs under age three. They may be caused by a viral infection. Unfortunately, these are very dangerous tumors. Typically, guinea pigs only live 2-3 weeks after clinical signs start.

T-cell lymphoma has been reported in guinea pigs. Typically, this is a poor prognosis.

How Veterinarians Diagnose Tumors and Cancers in Guinea Pigs

The diagnosis starts with a thorough physical exam by a vet. If any skin nodules are found, your veterinarian might perform a fine needle aspiration. This involves using a very thin needle to collect sample of cells from the tumor. Then the cells are examined under a microscope to see if they look abnormal and may indicate cancer.

The vet may also recommend a biopsy for skin tumors, either by taking a small tissue sample or completely removing the lump under anesthesia and sending it a pathologist to examine.

If your guinea pig has symptoms like trouble breathing, distended belly, not eating, and lethargy, your veterinarian will may perform tests such as bloodwork, x-ray, ultrasound, and CT scans to see how the organs are working.

If your veterinarian has found a tumor and is worried about it being malignant or metastasizing, they will likely perform an x-ray/CT scan or ultrasound to look for other spots where the tumor could have spread. This may include evaluating the lymph nodes, or even removing them, to look for any spread of the tumor.

Treatment of Tumors and Cancers in Guinea Pigs

Depending on the type of tumor, the most common treatment is removing through surgery. Chemotherapy and radiation might also be recommended if the tumor is malignant. Depending on the prognosis or stage of the tumor, palliative care might become the focus. This means keeping your guinea pig comfortable for as long as possible to maintain a good quality of life.

Recovery and Management of Tumors and Cancers in Guinea Pigs

Some tumors can be entirely removed and cured through surgery. After two weeks of rest and monitoring, your guinea pig can generally go back to her normal activities after following up with your veterinarian.

However, a tumor that is not entirely removed can grow back, even with supportive treatment.

Some malignant tumors can only be managed with chemotherapy, radiation, or surgery, which can be a long recovery process with frequent weekly or monthly trips to your veterinarian. Supplement with high fiber Oxbow Critical Care to offset any eating issues.

Depending on the severity of the disease, your veterinarian might recommend diet and lifestyle changes. Hence, it is vital to follow their instructions and check in if you have any questions or concerns.

To prevent reproductive tumors in your female guinea pig, it is best to get them spayed early.