Bone Cancer in Cats Caused by Hemangiosarcoma
Hemangiosarcoma is a type of cancer in cats that arises from blood vessels and can occur almost anywhere in the body. It is a highly metastatic form of cancer, meaning it spreads readily to other tissues. Usually when hemangiosarcoma occurs in bone it is due to metastasis from another site, although rarely, it may actually arise in the bone; the bone is then referred to as the primary site.
This tumor affects the bone much more rarely than osteosarcoma, but when it occurs in bone it can sometimes be very difficult to distinguish from the osteosarcoma. The cause of hemangiosarcoma is largely unknown. In people this type of cancer has been linked to exposure to vinyl chloride, a chemical agent.
The bone form of hemangiosarcoma is rare in cats, but can occur as a local extension of tumors of the soft tissues. It can affect the axial skeleton, which includes the bones of the spine, pelvis and skull, as well as the appendicular skeleton, which includes the arms and legs.
This is a lethal form of cancer in your pet. Average survival rate in animals with this type of cancer, even with treatment, is only months. In most cases, the tumor has already spread widely or will spread widely throughout the body, despite therapy and will continue to grow. When it primarily affects the bone, it can cause lameness and general debilitation of your pet during its development and progression.
What to Watch For
Lameness or pain, especially in the legs
Unexplained swelling of any bone
Broken bones without severe trauma
Diagnosis of Hemangiosarcoma of the Bone in Cats
Diagnostic tests are necessary to diagnose the tumor and define the extent of disease. Tests that your veterinarian may wish to perform include:
Complete medical history and physical exam
Radiographs (X-rays) of the affected body part
Radiographs of the chest/lungs
Abdominal (belly) radiographs
Cardiac (heart) ultrasound
Complete blood cell count (CBC)
Biopsy of the tumor
Treatment of Hemangiosarcoma of the Bone in Cats
Treatment may include the following:
Surgical removal of the tumor, which usually involves removing the affected bone
Radiation therapy as an alternate form of palliative treatment for pain relief in very select cases
Home Care and Prevention
Your veterinarian will most likely prescribe pain medication to ensure your pet’s comfort. These medications may be given prior to definitive diagnosis and/or after surgery. Medication will usually be in the form of pills or narcotic pain patches that are placed on the skin to release a constant level of medication across the skin.
You should limit your cat’s activity to minimize pain and to prevent what is called a pathologic fracture, which is an abnormal breaking of the bone due to the cancer weakening the bone. Your pet should not run, jump or play during this time. You should watch your cat carefully and give assistance when he climbs stairs.
Have your veterinarian evaluate promptly any unexplained bump or lameness that develops. Lameness is more likely to be associated with arthritis or injury to ligaments and tendons than cancer, but it is worth having your cat evaluated nonetheless.
If your cat does not improve with rest or anti-inflammatory drugs, radiographs of the affected part of the body may be indicated to exclude bone cancer as a cause of the lameness or pain.
Hemangiosarcoma, like other cancers, is not currently preventable.
In-depth Information on Hemangiosarcoma of the Bone in Cats
Hemangiosarcoma is a type of cancer that most commonly affects the spleen, liver and heart and typically causes bleeding from the ruptured tumor. Although it can arise in bone initially, this is rare. Most often when it occurs in bone, the tumor has spread there from another site in the body. Thus, if your cat is diagnosed with bone hemangiosarcoma it is vitally important that other more common sites of this tumor are excluded as the primary site.
As with most forms of cancer, very little is known about what causes hemangiosarcoma to develop. It is a highly lethal form of cancer and thus the diagnosis and treatment should be prompt and aggressive.
Related Symptoms or Diseases
Lameness. This is a general term used to describe pain or discomfort experienced when your pet moves normally or exercises minimally. Although your cat may develop lameness due to arthritis, ligament or tendon tears, or cartilage injury, lameness is also a cardinal sign of bone tumors. Therefore, any unexplained or chronic lameness in your pet warrants further investigation.
Pathologic fractures. If your cat experiences a fracture with minimal trauma, a pathologic fracture should be considered. Although fractures are most often a result of trauma, they can also occur in bones that have been weakened by cancer. Evaluating an X-ray may lead to the suspicion that the bone is abnormal; however, definite diagnosis of a tumor requires a biopsy. Pathologic fractures will not heal if fixed using standard techniques
Osteomyelitis. This is an infection in the bone and an uncommon condition that occurs as a result of infectious organisms such as bacteria or fungi getting into a bone. These organisms most commonly gain entrance to the bone through an open wound, open fracture or rarely through the blood (a blood borne infection). The appearance of osteomyelitis may be similar to some bone cancers because it often appears as a proliferative or fuzzy mass-like lesion on an X-ray. Differentiating these types of infection from bone cancer typically requires that a biopsy and a culture be performed.
Bone infarction. This is a very rare condition in which a blood clot blocks the blood supply to a bone, resulting in death of the bone. On an X-ray this appears as a lytic lesion, which means there is loss of bone, and is similar to the appearance of bone cancer.
Metastatic tumors to bone. Occasionally a bone cancer can be due to the metastasis or spread of cancer from a primary cancer elsewhere, most commonly mammary gland cancer. These types of cancers tend to have a distinctively different appearance on X-rays than primary bone tumors. Although their radiographic appearance may alert your veterinarian to their presence, a biopsy is still required for a definitive diagnosis.
It is important to distinguish tumors that have spread from other tissues to bone from those that arise in bone initially because the treatment differs. For metastatic tumors an attempt is made to determine the site of the primary cancer. If your pet is diagnosed with cancer, your veterinarian may wish to consult with an oncologist or cancer specialist to understand the specific behavior and treatment of the cancer.
Medical tests are needed to establish the diagnosis, exclude other diseases and determine the impact of hemangiosarcoma on your cat. Tests that your veterinarian may wish to perform include:
Complete physical exam. A thorough exam is necessary to not only localize the site of the cancer but also to assess your pet’s general health. Your cat’s general health may drastically influence the treatment options that your veterinarian recommends.
Radiographs (X-rays) of the affected body part. Although the appearance of a the bone on an X-ray may be suggestive of cancer, X-rays are not diagnostic of this condition.
Radiographs of the chest. Because the heart is a common location for this type of cancer, X-rays of the chest should always be taken prior to any type of surgery being performed. These radiographs will allow your veterinarian to assess the size of the heart and may give some indication as to whether masses are present, although echocardiograms are much better for seeing heart masses. Cats that already have evidence of heart or lung cancer are not good candidates for therapy because their disease is advanced.
Abdominal radiographs. X-rays are often taken of the abdomen to assess the outline of organs such as the liver, spleen, kidneys and lymph nodes. These are common sites for hemangiosarcoma.
Abdominal ultrasound (sonogram). This specialized procedure may require referral to radiology specialist. Ultrasound machines are computerized and have a probe that the doctor places on the surface of the skin. The probe transmits sounds waves, which bounce off the inside of the body and back to the probe. The computer then assembles these sound waves into a picture that shows internal body structures. It is a useful tool for helping to determine whether the cancer has spread to any of the soft-tissue body organs such as the liver, kidneys, spleen, intestines and lymph nodes. There is no risk to your pet with this procedure. It usually requires the hair on your pet’s belly to be shaved in order to get the best view through the skin.
Cardiac ultrasound. This is a similar exam as outlined in abdominal ultrasound. This test allows the veterinarian to examine the heart for the presence of any masses or other abnormality.
Complete blood cell count (CBC). This blood test counts the number of red blood cells (cells that carry oxygen in the body) and white blood cells (cells that fight infection). This is a standard test to screen your pet’s general heath and to ensure that it is safe to perform other procedures, such as surgery. However, it does not indicate if there is cancer in the blood.
Biochemical blood profile. This blood test assesses the general health of your pet’s organs by assessing the health of the liver and kidney function and measuring levels of electrolytes such as potassium and sodium. Dysfunction may or may not be associated with the spread of cancer to an organ.
Urinalysis. Like blood tests, a urine test provides your veterinarian information about your cat’s general health. Most importantly it assesses the health of the kidneys, but it also indicates the presence or absence of a urinary tract infection. The urine may be collected by catching some in a cup or by performing a cystocentesis, which passes a needle through the belly into the urinary bladder to remove a sample of urine.
Biopsy of the tumor. This is an essential procedure for definitive diagnosis of bone cancer. Because it is painful to biopsy bone, this procedure is done under anesthesia. Your veterinarian or a veterinary specialist such as an oncologist will insert a large needle into the affected area of bone to remove a core of tissue. The tissue sample is then submitted to a pathologist to determine the form/type of cancer. There is a minimal risk of fracturing the bone with this procedure, but because it is essential for the diagnosis, the risk is worth taking. Your pet is likely to be in pain after this procedure and pain medications are often administered. A patch may be placed on the skin to allow absorption of a constant level of narcotic.
Surgery. When it can be done, removal of the tumor en bloc, which means along with normal surrounding tissues, is the best way of dealing with hemangiosarcoma. Because bone hemangiosarcoma most commonly metastasises from another site, it is imperative that a thorough diagnostic test series be performed prior to surgery. Your veterinarian may refer you to a surgical specialist for these procedures. Surgery is the best means of removing the cancer and for most pets it results in abolishing the pain caused by the cancer. Depending on the extent of surgery, your pet may need to spend a few days in the hospital post-operatively where he can receive narcotic pain medications and fluid supportive care and be allowed to rest.
Chemotherapy. Because this cancer tends to spread very early, chemotherapy is usually prescribed. Chemotherapy usually starts in the postoperative period once healing has occurred and the sutures/staples have been removed. Chemotherapy drugs are typically given intravenously and their administration usually follows a set schedule of every three weeks for a total of four to six doses. Many different types of chemotherapy drugs are available, and your veterinarian is likely to refer you to a veterinary oncologist in your area who can advise you on treatment options.
One of the most commonly utilized drugs for hemangiosarcoma is adriamycin (Doxorubicin). However, every oncologist has a preference and may select certain drugs, or combinations of drugs, based on your pet’s general health and the extent of disease. The common side effects include a decrease in white blood cell count approximately seven to 10 days after each treatment, nausea, vomiting and/or diarrhea. Each of these drugs may also have unique side effects which your oncologist will discuss with you.
Radiation therapy. This is a type of treatment in which a beam of radiation is directed at the tumor, resulting in palliative treatment or pain relief. It is a highly-specialized treatment and is available in select referral veterinary centers. It may be considered if your pet has existing conditions that disqualify him for surgery. Your cat will not experience side effects similar to those typically associated with radiation therapy in humans. The oncologist or radiation oncologist prescribing these treatments will discuss further details.
Pain medications. For those electing to not pursue any of the above treatments, the administration of both narcotic and non-narcotic anti-inflammatory drugs can help make your cat more comfortable.
Follow-up Care for Cats with Bone Hemangiosarcoma
Optimal treatment of your cat requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your cat does not improve rapidly.
You should limit your cat’s activity to minimize pain and to prevent a pathologic fracture prior to definitive therapy. Your cat should not run, jump or play during this time and you should watch him carefully and provide assistance when climbing stairs or getting in and out of the car.
Administer all prescribed medications as directed. Alert your veterinarian if you are experiencing problems treating your cat. Your veterinarian should prescribe pain medications to ensure your pet’s comfort either prior to definitive diagnosis and/or in the aftercare period from surgery. This can be through the use of pills or narcotic pain patches that are placed on the skin and release a constant level of pain medication across the skin.
After surgery, you will need to limit your cat’s activity for at least 10 to 14 days or until the surgical site heals and the sutures or staples are removed. During this time, your cat should not climb stairs unattended, jump or play. You will also need to keep the surgical site clean and dry. Most cats go home on some form of pain control. Any questions you have about your cat during the postoperative period should be addressed with your veterinarian immediately.
Once healing has occurred, your cat can get back to exercising gradually. It may surprise you how quickly your pet begins to move about after surgery, but many feel so much better once the cancer is removed that they are up and acting normal within two to three days after surgery.
Whenever your pet has been diagnosed with hemangiosarcoma, you should be aware of the potential of the cancer recurring somewhere else in the body. Your pet may also suffer bleeding episodes if one of these tumors ruptures. If this happens you should be prepared for the possibility of weakness and an acute collapse.