Bone Tumor (Hemangiosarcoma) in Cats

4 min read

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.



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