Vascular Tumors Affecting the Skin
What are vascular tumors of the skin?
Vascular tumors are tumors that develop from blood vessels. When involving the skin, they develop from the blood vessels of the skin. Essentially, wherever there are blood vessels, there is the chance for vascular tumors to develop. Some tumors (called hemangiomas) behave in a benign manner, whereas others (called hemangiosarcomas) tend to spread.
What causes this type of cancer?
The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Very few tumors and cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary. Although the cause of vascular tumors in dogs and cats has not been determined, there appears to be a greater incidence of hemangiosarcoma of the skin in lightly pigmented and sparsely haired dogs, which may indicate that ultraviolet light (sun) exposure may play a role in the development of these tumors.
What are the clinical signs of this type of tumor?
Vascular tumors of the skin may arise anywhere on the body and appear as a firm and raised lump on or under the skin. They may be red and look like a blood blister or may be the same color as the skin. Sometimes they have a bruised appearance or change in size due to bleeding within them.
Hemangiomas may ulcerate and bleed; hemangiosarcomas may bleed into the surrounding tissues. If the bleeding of a hemangiosarcoma is confined in the skin or underlying tissues, excessive bruising, pain, weakness, reluctance to stand or go for walks, pale gums, or collapse may occur.
If a tumor develops in a region such as the armpit or between the legs, there may be pain or discomfort when moving.
A vascular tumor may appear ’innocent’ or inconsequential but be quite the opposite. For this reason, it is best to have any changes in the skin evaluated by your veterinarian as soon as you notice them. Image via Wikimedia Commons/Joel Mills (CC BY-SA 3.0.)
How is this type of tumor diagnosed?
This type of tumor is typically diagnosed via a tissue biopsy or surgical removal of the entire tumor. A biopsy is a surgical excision of a piece of the tumor. Pieces of the tumor are then examined by a veterinary pathologist under the microscope. This is called histopathology. Histopathology is not only helpful to make a diagnosis but can indicate how the tumor is likely to behave.
Given that these are vascular tumors, the biopsy or surgical site could bleed excessively.
The prognosis is based on the results of the histopathology examination. Depending on how deeply the tumor extends into the surrounding tissues (i.e., isolated to the skin or spread to the underlying muscle), the prognosis varies.
"The tumor can develop at any location on or under the skin."
Staging (searching for potential spread to other locations in the body) should be pursued with any diagnosis of hemangiosarcoma. Staging could include bloodwork, checking the urine (urinalysis), checking your pet's ability to clot, X-rays, and an abdominal ultrasound. If any lymph nodes are found to be enlarged on physical examination or with the above diagnostics, a sample may be obtained to look for spread of the cancer.
How does this type of cancer typically progress?
Hemangiomas are the benign form of the disease and have an excellent prognosis. Although hemangiomas can ulcerate, or rupture within the skin, causing bleeding, and possibly mild discomfort, they are not known to spread.
Hemangiosarcomas have a more guarded prognosis. With bleeding into the underlying tissues, you may see bruising or discoloration of the skin surrounding or at the location of the mass. If the mass is large enough, or in an area that affects your pet's mobility, lameness or pain in the region may be noted.
Typically, hemangiosarcomas are locally invasive, meaning they will continue to grow in the region that they are found. However, depending on the results of histopathology, and how deep the tumor extends, spread to other organs is possible. With those confined to the skin only, the metastatic rate (spread) is about 30%, whereas those with involvement of the underlying muscle, the rate increases to 60%.
What are the treatments for this type of tumor?
Surgery is the recommend treatment for vascular tumors of the skin. Surgery is usually curative for hemangiomas and the prognosis is excellent.
With hemangiosarcomas, depending on the tumor location, physical exam findings, and staging, it may be recommended to perform a CT scan (for a more detailed image) to determine how far the tumor extends prior to attempting surgery. If surgery is not an option, radiation therapy may be recommended. After surgery or radiation therapy, chemotherapy may be recommended.
Is there anything else I should know?
If you pet has been diagnosed with a hemangiosarcoma, the mass could rupture and cause further bleeding, putting your pet at immediate risk. Therefore, it is very important that your pet be kept quiet and monitored very closely for any of the signs listed above. Typically, once a diagnosis has been obtained, it is best not to wait to pursue therapy.
"If you pet has been diagnosed with a hemangiosarcoma, the mass could rupture and cause further bleeding, putting your pet at immediate risk."
Anticoagulant medications or medications that may increase the risk of bleeding (such as nonsteroidal anti-inflammatories) should be avoided prior to surgery.
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