Heart Tumor (Rhabdomyoma) in Dogs

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Rhabdomyoma in Dogs

A rhabdomyoma is an extremely rare, benign, non-spreading, cardiac muscle tumor that occurs only half as often as its malignant version: rhabdomyosarcomas, an invasive, metastasizing (spreading) tumor.

Rhabdomyomas are usually found in the heart, and are suspected of being congenital in origin (present at birth). This type of tumor does not become malignant, nor does it metastasize through the body. They are very rarely found outside of the heart, but do occur in other places of the body on occasion. They have been reported in the tongue, and in the larynx (voice box) in dogs.

Rhabdomyoma can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.

Symptoms and Types

  • Rhabdomyoma in the heart:
    • Usually no symptoms
    • Rarely, there will be signs of right-sided congestive heart failure (CHF) due to obstruction
  • Rhabdomyoma outside the heart:
    • Localized swelling


Idiopathic (unknown)


You will need to provide a thorough history of your dog's health leading up to the onset of symptoms. From there, your veterinarian will perform a complete physical exam on your dog, with a blood chemical profile, a complete blood count, a urinalysis, and an electrolyte panel. Your veterinarian will use the results of the bloodwork to confirm, or rule out, other diseases. Bloodwork will typically appear normal in patients with a rhabdomyoma, since the tumor is relatively harmless.

X-ray imaging, and an echocardiogram of the heart may help your veterinarian to diagnose a rhabdomyoma. Additional examination using an electrocardiogram will note heart arrhythmias (rhythm abnormalities). For a definitive diagnosis, an examination of tissue from the tumor (biopsy) can be performed.

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