Heart Tumors in Cats

By PetMD Editorial on Feb. 10, 2009

Myocardial Tumors in Cats

Myocardial tumors are rare types of tumors that affect the heart. When they do occur, they tend to occur in older animals. A myocardial tumor can take either of two forms: a benign tumor, which is a mass of tissue that does not metastasize; and a malignant tumor, which does metastasize throughout the body. A benign tumor might be categorized as a hemangioma – a harmless growth consisting mainly of newly formed blood or lymph vessels. Conversely, a malignant tumor might be categorized as a hemangiosarcoma - a are and abnormal, rapidly reproducing tissue growth that arises from the blood vessels in the heart.

A tumor that arises from the fibrous tissue, like heart valve tissue, is referred to as a fibroma if it is benign, and a fibrosarcoma if it is malignant. There are also tumors that develop in the softer, connective tissue in the upper chambers of the heart (atria). Benign tumors of this sort are termed myxomas; myxosarcomas when they are malignant. One particular type of tumor that is always malignant is the rhabdomyosarcoma – a tumor that arises from the skeletal muscle in the heart.

There are also tumors that can spread to the heart secondarily. Some tumors which do not arise in the heart, but which spread to it, are lymphomas - malignant tumors of the lymph nodes; neurofibromas - benign tumors of nerve fiber origin; granular cell tumors – of unknown origin, which can be malignant or benign; and osteosarcomas - malignant tumors that originate in the bone.

Symptoms and Types

Symptoms are dependent on what type of tumor is in the heart, and where in the heart it is located:

  • Heart rhythm abnormalities (cardiac arrhythmia)
  • Heart murmurs
  • Enlargement of the heart
  • Sudden heart failure
  • Signs of heart failure due to heart tumor:
    • Coughing
    • Difficulty breathing, even while at rest
    • Sudden collapse
    • Exercise intolerance
    • General fatigue
    • Fainting
    • Lack of appetite
    • Bloated, fluid filled abdomen



The causes for myocardial tumors are still unknown.

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Your veterinarian will perform a thorough physical exam on your cat, including a baseline blood work profile. This will include a chemical blood profile, a complete blood count, a urinalysis, and an electrolyte panel. Chest x-rays and ultrasound imaging will allow your veterinarian to visually examine the heart, so that a complete assessment can be made of the heart, and any masses that are present within it. An electrocardiogram (ECG, or EKG) recording can be used to examine the electrical currents in the heart muscles, and may reveal any abnormalities in cardiac electrical conduction (which underlies the heart’s ability to contract/beat). Your veterinarian may also need to take a surgical tissue sample of the mass for biopsy.


Even if the mass in the heart is extensive, or has begun to spread through the body, surgical resection is still the recommended treatment of choice for most heart tumors. This holds even if the surgery will not cure the condition. But, if the tumor is benign, surgical resection may be curative. Chemotherapy can be administered in the case of malignant heart tumors, but unfortunately, in many cases patients will die in spite of treatment.

Living and Management

Your veterinarian will schedule follow-up appointments for your cat in order to perform serial heart ultrasounds. These examinations will help your doctor to follow the progress of your cat's condition as well as to check the heart muscle for signs of doxorubicin toxicity – if doxorubicin has been prescribed as part of a chemotherapeutic program. Doxorubicin is an effective drug for treating malignant cancers, but one of the negative side effects is that it can damage heart muscle. Your veterinarian will also take chest x-rays at each visit to make sure the tumor has not spread. The final prognosis for most malignant myocardial tumors is guarded to poor.

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