Skin Cancer (Hemangiosarcoma) in Dogs

A hemangiosarcoma is a malignant form of cancer that originates from the cells lining the blood vessels. It causes fast growing but fragile tumors that are prone to rupture, and when they rupture they can bleed profusely. When these tumors occur on the skin they are called dermal hemangiosarcomas and when they occur underneath the skin they are known as subcutaneous or hypodermal hemangiosarcomas. When these tumors form internally there is a very poor prognosis, with very few patients living more than a year after diagnosis. With surgical removal and aggressive chemotherapy treatment, the prognosis is somewhat improved for the dermal and subcutaneous forms of the disease.

Hemangiosarcoma is an aggressive and malignant form of cancer that originates from the cells lining the blood vessels. Aggressive treatment may prevent the spread of tumors on the skin.

Many of the symptoms of hemangiosarcoma in dogs may arise from blood loss due to the internal rupturing of one of the tumors. 

• Collapse
• Depression
• Difficulty breathing
• Lack of appetite
• Lethargy
• Lumps on or directly under the skin
• Pale mucous membranes
• Shock
• Ulcerated sores on skin
• Visible bleeding
• Vomiting
• Weakness 

Additional gastric and cardiac symptoms can arise if the cancer has spread to the spleen, heart, or liver. 

Types

Dermal

• These hemangiosarcomas grow on the skin itself, presenting as red or purplish-black tumors on the surface of the skin
• The color comes from the blood that is encased in the hemangiosarcoma
• These tend to be located on the areas of the body that receive the most solar radiation

Subcutaneous (hypodermal)

• These form directly under the skin and can be found anywhere on the body, and can appear very bruise like or may appear raised, but otherwise normal
• The lesions can be either soft or firm
• Subcutaneous hemangiosarcomas are more likely to metastasize than dermal hemangiosarcomas

The causes of any cancer can be ambiguous but there are some things that may trigger the formation of hemangiosarcomas. Dermal hemangiosarcomas, in particular, have a link to solar radiation and are more common in dogs with short hair and dogs with white hair. Using sunscreen formulated for dogs, especially for dogs with short or sparse coats, may help prevent their formation. 

• Age (average age 8-11 years old) 
• Breed predisposition: Boxer, Dalmatian, Doberman Pinscher, German Shepherd, Golden Retriever, Labrador Retriever, Pointer, Rottweiler, Schnauzer
• Exposure to solar radiation

Your veterinarian is likely to start with a verbal history from you and a physical examination of the masses or lesions and will also want to get a sample of the tissue so that it can be examined more closely. A complete blood count, biochemistry profile, and urinalysis are also likely to be done at this time as well. As hemangiosarcoma is a malignant cancer, your veterinarian may want to run some testing to see if it has spread to any internal organs before making any recommendations. Other types of tests that may be recommended are:

• Cardiac ultrasound to detect tumors that have formed on the heart
• Clotting tests to assess organ function
• ECG to detect abnormal heart rhythms 
• Radiographs of the abdomen and chest to detect masses in the lungs, spleen or liver

The final diagnosis will be made through a biopsy of the affected tissues. Tumors located on or under the skin are often excised with the surrounding tissue for further testing.

If your dog is already showing signs of shock or excessive bleeding, supportive treatment such as IV fluids to prevent dehydration will be administered to give the patient the best chance for survival. 

With the dermal and subcutaneous forms of this cancer, removing the tumor and surrounding tissue can sometimes halt or slow the progression of the disease. As both of these forms have the potential to spread quickly surgical removal should be done as soon as possible in an attempt to prevent this from happening. Chemotherapy is generally the next type of treatment to consider. Dogs tolerate chemotherapy better than most humans and only around 5% require hospitalization from the treatment itself. There is less reported hair loss in dogs than in people, but some breeds (English Sheepdog, Lhasa Apso, Maltese, Schnauzer, Shih Tzu, and Poodle) are more prone to hair loss.

These treatments may extend the life of your pet, and although prognosis is quite poor when cancer has invaded the internal organs, it is somewhat improved for the subcutaneous and dermal forms.

After any excision, it is important to keep the surgical site clean and free from debris. You will need to keep your pet from interfering with the site, and examine it for swelling, bleeding or pus, and to ensure that the stitches are intact. Complications from chemotherapy can arise, so your veterinarian will probably want to do regular checks on your dog’s liver and kidney enzyme levels. Pets are often sent home the same day after chemotherapy, and although most of the drug is metabolized within just a few hours, some remnants of it can remain in the blood for a few days. It is important to use gloves when dealing with bodily fluids and maintain good hand washing hygiene. Children, pregnant and nursing women and immunocompromised adults should avoid contact with the bodily fluids during that time. Your pet should be monitored closely for additional tumors during and after their chemotherapy treatments.