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Cancer in Guinea Pigs

To keep your guinea pig healthy, all she needs is a clean and appropriate home, plenty of fresh water with supplemental vitamin C, freshly milled guinea pig pellets and fruits and vegetables. For most guinea pigs, this results in a happy healthy guinea pig that can live up to 5 to 8 years. Unfortunately, cancer occurs in guinea pigs just as it does in other animals and people.


Lymphosarcoma is the most common tumor of guinea pigs. It is considered a cancer arising from the blood and is thought to be caused by a retrovirus. Affected guinea pigs often have enlarged lymph nodes in their neck and have a scruffy appearance. As the disease progresses, other lymph nodes become enlarged and the liver and/or spleen may swell. Some guinea pigs develop leukemia.

Lymphosarcoma is diagnosed through evaluation of a lymph node aspirate or biopsy. Animals with leukemia have a very high white blood cell count. Affected guinea pigs have a poor prognosis and most do not do well with treatment. High doses of the steroid prednisone may be attempted. Unfortunately, most guinea pigs worsen over the course of 2 to 5 weeks and either expire or are euthanized.

Lung Cancer

Cancer is often divided into those cancers arising from the blood and those that do not. Lung cancer is one of the most common types of cancer in the guinea pig that does not arise from the blood. The most likely cause of lung cancer in guinea pigs is a benign adenoma. Since this type of tumor is benign, it does not spread but it can still be life-threatening. The tumor usually begins on the edges of the lungs and slowly invades the lung tissue. By the time it is diagnosed, a significant amount of the lung tissue has been destroyed and the guinea pig is struggling to breathe. At this point, little can be done.

The reason this disease is often not treatable is that routine X-rays are rarely taken of healthy older guinea pigs. If X-rays of the chest are taken and a small mass or tumor is detected, surgical removal can be performed. This removes the cancer and is considered curative. If the disease is diagnosed after a majority of the lung tissue has been involved, surgical removal is not possible.

In a few cases, a malignant adenocarcinoma has been diagnosed. These are aggressive tumors that can spread throughout the body. There is no cure.

Breast Cancer

Breast cancer, also called mammary gland cancer, is not common but can occur in both males and females. It is most often found in older guinea pigs and is rarely, if ever, diagnosed in guinea pigs under three years of age.

The guinea pig has two breasts located between the back legs. When affected with cancer, tumors often only develop in one breast and are usually benign fibroadenomas. These tumors do not spread to other parts of the body and surgical removal of the affected breast is usually curative. About 30 percent of the time, the tumor is a malignant adenocarcinoma. These spread throughout the affected breast but do not often spread throughout the body. Surgical removal is usually curative.

Skin Cancer

Guinea pigs are also prone to certain skin tumors. The most common is the basal cell tumor, often found on the skin of the back or rear legs. This is a slow growing tumor that is usually oval in size and firmly attached to the overlying skin. Over time, the tumor may develop an open wound that drains thick pus. At this stage, the tumor may become infected.

Treatment for basal cell tumor is surgical removal, preferably before an open sore develops. This usually results in a cure since this type of tumor does not frequently spread and recurrence is rare. There may be a genetic component to this tumor and it may run in certain families.

Bone Cancer

Osteosarcoma is an uncommon cancer in the guinea pig. Of all the different types of cancer affecting guinea pigs, osteosarcoma is diagnosed only about one percent of the time. Affected guinea pigs often have painful swellings on the leg bones. The best treatment is amputation of the bone but a cure is unlikely. Osteosarcoma is an aggressive cancer that readily spreads. It is very rare to diagnose bone cancer in a guinea pig less than one year of age.

Bladder and Uterine Cancer

Cancer of the bladder and uterus are relatively uncommon. The most common sign associated with these cancers is bloody urine. If diagnosed with bladder cancer or uterine cancer, treatment usually involves feeding iron rich foods and supplementing with B vitamins. This can help the guinea pig if he/she becomes anemic from blood loss. If the cancer or blood loss is severe, euthanasia is often recommended.