Canine hemangiopericytoma is a cancerous tumor that begins in the pericyte cells surrounding small blood vessels in the body. Pericytes are embryonic, nonspecialized cells that normally take on a specialized function in the body. In hemangiopericytoma, damaged versions of these cells form tumors. Tumor regrowth is common, but the malignant cancer rarely metastasizes to other areas of the body. If these tumors are not treated, they can eventually grow large enough to cause disfigurement or death.
Hemangiopericytoma tumors usually grow on the limbs or trunk; they can take weeks or months to develop. They appear as soft, fluctuant or firm masses. They may appear as bald spots, sores or ulcers, or may cause different skin pigmentation in the area of the tumor. These tumors are more common in large-breed dogs.
If you notice new bumps or nodules on your dog, contact your veterinarian to schedule an examination. The veterinarian will perform a thorough examination, including blood and urine tests. He will take a tissue sample of the tumor for a biopsy and definitive diagnosis. X-rays, CT scans or magnetic resonance imaging tests will help determine how deep the tumor is rooted, helping the veterinarian determine the best course of treatment.
Surgery is necessary to remove the tumor and the surrounding tissue. Because the hemangiopericytoma tumor is likely to grow back in the same location, treatment after surgery focuses on preventing regrowth. Radiation therapy offers a cure rate of 80 percent to 90 percent; however, adequate treatment requires 15 to 18 treatments and is costly. An option is to wait for regrowth and repeat tumor removal surgery. One problem with this is that, when the tumor regrows, it is often more deeply rooted and more difficult to remove. In older dogs, leaving regrowth tumors alone is another option because of their slow growth rates. If complete removal of a tumor is not possible, low-dose chemotherapy can slow progression.
A last-resort available option, providing a cure of sorts, is to allow amputate the affected limb. While this may seem extreme, amputation surgery is less expensive than radiation therapy treatments and, because hemangiopericytoma rarely metastasis to other areas of the body, amputation removes the risk of continued tumor growth and death. Most dogs recover well from amputation surgery and learn to compensate for the lost limb, living full and happy lives. Discuss all possible treatment options with your veterinarian.