*Warning - Image of surgically removed uterine cancer included.* Like all animals, guinea pigs can develop cancer. As guinea pigs are living longer, with good veterinary care; and owners are becoming more observant of their conditions, cancers are being diagnosed more frequently. Cancers can be either benign (meaning they do not have the potential to spread elsewhere) or malignant (which can spread elsewhere). Benign cancers carry a good prognosis; however, malignant cancers carry a much more guarded prognosis.
The cancers I see most commonly in guinea pigs in practice are lymphoma, mammary tumours, skin tumours, and uterine tumours.
Lymphoma, also known as lymphosarcoma, is the most commonly diagnosed cancer of guinea pigs. The condition has sometimes also been referred to as cavian leukaemia in some texts. Both are cancers of blood cells but lymphoma mostly affects lymph nodes and leukaemia mostly affects the bone marrow. The clinical signs are similar in each, and include lethargy, anorexia, laboured breathing (dyspnoea), a ruffled unkempt coat; in lymphoma cases enlarged lymph nodes throughout the body and an enlarged liver and spleen are also seen.
Diagnosis of lymphoma can often be achieved by sampling an enlarged lymph node, however, with leukaemia a blood sample is often required. It is thought that cavian leukaemia can be transmitted by a virus, known as a retrovirus. It is thought that transmission is primarily mother to young (known as vertical transmission) but transmission between unrelated individuals may also be possible (horizontal transmission). This cancer carries a very poor prognosis.
Chemotherapies are yet to be well developed in guinea pigs but there are some drug options, including prednisolone, cyclophosphamide and L-asparaginase. Unfortunately, even with these chemotherapies life expectancy is likely only to be weeks to months.
With the other common cancer types in guinea pigs, a solid mass can be felt. All of these cancers have both malignant and benign versions. The only way of knowing which one you are dealing with is to take a sample of the mass. This can be achieved by a fine needle aspirate (taking a sample through a needle, this can often be done conscious) or a biopsy (taking a piece of tissue, this will require general anaesthetic). Usually the treatment of choice in these cases will be surgical removal of the mass. The image below is of a uterus and ovaries removed from a guinea pig who had a uterine tumour. The guinea pig recovered well from surgery.
Not all masses are malignant cancers, some are benign and some won't be cancer at all. If you notice any swellings or lumps on your guinea pigs, they should be investigated by a vet.