Heart Tumors in Cats

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.


A bundle of fibers that are used in the process of sending impulses through the body


The prediction of a disease’s outcome in advance

skeletal muscle

A muscle that is involved in voluntary movement


An in-depth examination of the properties of urine; used to determine the presence or absence of illness


Something that becomes worse or life threatening as it spreads


A tumor made up vascular tissue


A record of the activity of the myocardium


The process of removing tissue to examine it, usually for medical reasons.


Appearing like particles or small granules in texture


A neoplasm made of new blood vessels


Not being able to cause harm; the opposite of malignant.

lymph nodes

Small structures that filter out the lymph and store lymphocytes

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