Bone Tumor (Hemangiosarcoma) in Cats

By PetMD Editorial on Jul. 31, 2009

Hemangiosarcoma of the Bone in Cats

Hemangiosarcoma is a fast spreading tumor of the endothelial cells, which line the interior surface of the body's blood vessels, including the arteries, veins, intestinal tract, and the bronchi of the lungs.

The integrity of the bone may be compromised by the tumor, and fractures in the bone, absent an accident related trauma to the body, are characteristic of bone cancer. Most commonly, this type of tumor is found on the limbs or ribs, but it can occur in other locations as well.

As with many types of cancers, hemangiosarcoma is usually diagnosed in cats older than 17 years.

Symptoms and Types

  • If tumor is on leg, lameness and/or swelling
  • Fracture due to weakness in bone
  • Swelling at affected site
  • Difficult breathing may be present if tumor involves the rib
  • Pale mucous membranes (i.e., nostrils, lips, ears, genitals)
  • Anemia due to blood loss from ruptured tumor


The exact cause for hemangiosarcoma of the bone is still unknown.


Your veterinarian will perform a thorough physical exam on your cat, including a complete blood profile, a chemical blood profile, a complete blood count, and a urinalysis. These tests may indicate whether any of the organs are being affected, and whether any other conditions are present. Some of the conditions that may be concurrent with hamangiosarcoma are regenerative anemia, which is determined by an abnormally high number of immature red blood cells (meaning that the body is replacing lost red blood cells at a high rate); an abnormally low level of protein in the blood (hypoproteinemia); an abnormally high white blood cell count (leukocytosis), which can be indicative that the body is fighting off a diseased condition; a low level of platelets in the blood (thrombocytopenia), which are responsible for blood clotting; and blood cells of unequal or abnormal size (anisocytosis and poikilocytosis, respectively).

Radiographic studies of the affected bone will also reveal valuable information to help your veterinarian in the diagnosis of this tumor. Computed tomography (CT) scans can help to determine the extent of bone involvement and also help your veterinarian in planning an effective surgery. Biopsy may be attempted for a definitive diagnosis, but this may not be practical for this type of tumor, since it originates in the vessels.

A confirmative diagnosis may be based on finding spaces within the vessels that are filled with red blood cells, clots, dead cellular debris, and variable tumor cells.




Aggressive surgery remains the method of choice in the treatment of this tumor. The tumor, and possibly the surrounding area, will need to be removed entirely. If the tumor is occurring on a limb, the affected limb will most probably be amputated, a surgery which most cats recover from well. An axial tumor – one that is affecting the area of the head or trunk – may be more difficult to treat. Chemotherapy along with surgery is the recommended treatment plan.

Living and Management

Your veterinarian will set up a schedule for progress evaluation visits, starting from the first month after initial treatment and every three months following. Chemotherapy medications have the possibility of toxic side effects, so your veterinarian will need to closely monitor your cat's stability, changing dosage as necessary. Routine x-rays will be taken of the chest, heart and abdomen to check for recurrence and progress.

After surgery, you should expect your cat to feel sore. Your veterinarian will give you pain medication for your cat to help minimize discomfort. Use pain medications with caution; one of the most preventable accidents with pets is overdose of medication. Follow all directions carefully. You will need to limit your cat's activity while it heals, setting aside a quiet place for it to rest, away from household activity, children, and other pets. You might consider cage rest for your cat, to limit its physical activity. Your veterinarian will tell you when it is safe for your cat to move about again. Most cats recover well from amputation, and learn to compensate for the lost limb.

It is important to monitor your cat's food and water intake while it is recovering. If your cat does not feel up to eating, you may need to use a feeding tube so that it is getting all of the nutrition it needs to completely recover. Your veterinarian will show you how to use the feeding tube correctly, and will assist you in setting up a feeding schedule. While your cat is in the process of healing, you may set the litter box up closer to where your cat rests, and make it so that it is easy to get in and out of the box.

Each cat is different, and some will survive longer than others, but the average time of survival after surgery is six months. Less than ten percent will survive for one year after surgery.

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