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Hemangiosarcoma
Nancy McDonald, RN, BSN
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Hemangiosarcoma, also known as malignant hemangiothelioma or
angiosarcoma, is a very aggressive, high-grade soft tissue cancer of
vascular tissue with the skin, heart and spleen the most common
areas affected. Dermal (skin) hemangiosarcomas are less aggressive
than visceral tumors with lower metastatic potential and longer
survival times. Visceral (internal) tumors are highly malignant
tumors with a poor prognosis. This highly malignant cancer
originates in the lining of the blood vessels, spreads rapidly,
causing tumors almost anywhere in the body. Insidiously, it attempts
to build its own blood vessel network, making blood-blister-like
formations which disrupt normal organ function. A common form of
cancer in dogs, hemangiosarcoma affects mostly older, large breed
dogs although all dogs, including young, can be affected. Males tend
to have a higher rate of diagnosis than females, with German
Shepards and Golden Retrievers more affected than other breeds. This
cancer has not been reported in large numbers in Bichons, though it
has occurred.
Dermal (skin) hemangiosarcoma often appears as a rosy red or purple
to black growth on the skin, which may be raised. Associated with
sun exposure, this form of tumor tends to appear on non-haired or
sparsely haired areas like the abdomen. Dogs with short white-haired
fur (such as Dalmatians, Whippetts, Italian Greyhounds, Bull
terriers) are prone to this tumor development. Although
solar-induced canine dermal hemangiosarcomas generally do not have
as aggressive biologic behavior as visceral tumors and can be
controlled with topical chemotherapy as needed, numerous lesions may
continue to appear over a period of several years. Because 30% of
all dogs with dermal hemangiosarcoma develop metastatic disease, it
is important to remove the growths promptly.
The overlying skin on top of a hypodermal (under the skin)
hemangiosarcoma is often totally normal. When the tumor is removed,
a dark red blood growth is found. Because 60% of hypodermal
hemangiosarcomas spread internally, it is important to run further
tests, chest x-rays, ultrasound of the abdomen, and ultrasound of
the heart to determine if the cancer has spread.
Visceral (internal) hemangiosarcoma accounts for 2% of all reported
malignancies and up to 5% of all noncutaneous tumors in dogs.
Although these numbers seem small, the impact is significant since
this form of cancer kills. The spleen and right atrium of the heart
are the most common sites of occurrence of visceral hemangiosarcom.
The spleen is seated deeply within the abdomen and tends to go
unnoticed unless it develops a growth of unusual size. Because the
spleen is especially vascular, any growth, regardless of whether it
is benign or malignant, has a tendency to break open and bleed
profusely. If the splenic tumor is found early and is not too large,
a splenectomy (removal of the spleen) may be preformed. Although a
splenectomy certainly protects from this life-threatening sudden
bleed, splenic hemangiosarcoma is still a rapidly spreading
malignancy. 25% of dogs with splenic hemangiosarcoma also have a
heart-based hemangiosarcoma.
Like the splenic hemangiosarcoma, the heart-based hemangiosarcoma
tends to exert its life-threatening effects by bleeding. The heart
is enclosed in a sac called the “pericardium.” When the
hemangiosarcoma bleeds, the blood fills up the pericardium creating
so much pressure that the heart can no longer function. If allowed
to progress, results are a circulatory collapse called a
“pericardial tamponade” and can only be relieved by withdrawing the
excess fluid from within the pericardium. At the time the
heart-based hemangiosarcoma is discovered, 63% have evidence of
matastatic tumor.
The most common blood disorder associated with hemangiosarcoma
tumors is disseminated intravascular coagulation (DIC), blood
clotting that occurs inappropriately inside the blood vessels. This
process uses up all the blood clotting elements rapidly. Dogs with
this condition usually have platelet deficiencies, increased blood
clotting times, decreased fibrin content in the blood and an
increase in fibrin degradation products. This is the cause of death
in most dogs affected with hemangiosarcoma. Bleeding disorders
associated with hemangiosarcoma are sometimes confused with
immune-mediated hemolytic anemia because the type of anemia caused
by the two conditions is very similar and early clinical signs are
often very similar. Also, due to the thrombocytopenia (platelet
deficiency), immune-mediated thrombocytopenia may be suspected.
Visceral hemangiosarcomas leave little warning they are present
prior to causing severe clinical signs of disease. A common estimate
of the average time from discovery of the tumor until death occurs
is six to eight weeks, but death occurs more rapidly than this in
some cases. Visible bleeding, usually in the form of nosebleeds, and
signs associated with blood loss, such as tiring easily, episodes of
unexplained weakness, pallor to the mucus membranes of the mouth and
eyes, increased respiratory rates, abdominal swelling and depression
are the most common presenting signs for hemangiosarcoma. A few dogs
just suddenly die with no clinical signs having been noted. A large
splenic hemangiosarcoma can be found on physical exam. Heart-based
hemangiosarcoma is hard to find on physical exam and can be missed
on x-rays. If bloody fluid is aspirated from the abdomen,
hemangiosarcoma is suspected. Sometimes hundreds of small tumors are
spread throughout the body, and surgical exploration or an autopsy
are the only ways to identify the problem.
Hemangiosarcoma is primarily treated with a combination of surgery
and chemotherapy and some radiation. The drug of choice is
Doxorubicin and Cyclophosphamide. Surgical removal alone is often
not very rewarding. Because of the high risk of metastasis, the
average survival time without chemotherapy is one to two months,
with less than 10% of these dogs living a year. With surgical
removal and accompanying chemotherapy, the average survival time
increases to five to seven months. However, 90% of theses dogs still
do not survive more than a year after initial treatment. Skin-based
hemangiosarcoma appears less likely to be metastatic when initially
diagnosed, and surgical removal of the skin-based tumors can be
curative. However, chemotherapy is often recommended in addition to
surgery.
In summary, hemangiosarcoma tumors cause significant bleeding
extra-vascular (outside the blood vessels) and clotting
intra-vascular (within the blood vessels) and spread early; survival
times are usually short. Surgery is helpful to prevent massive blood
loss, but rarely affords a cure. Chemotherapy can be helpful, but
even with aggressive treatment, survival beyond one year is
extremely rare. Only superficial skin tumors allow long-term
survival with surgery alone, although recurrence is likely. As
hemangiosarcoma is rare in humans, little research has been funded.
However, the development of new chemotherapy drugs in association
with early detection could prove to increase survival times.
Lippincott’s Nursing Drug Guide, 2006
Taber’s Cyclopedic Medical Dictionary
www.marvistavet.com/html/hemangiosarcoma.html
www.vetinfo.com/dencyclopedia/dehemsarcoma.html
www.caninecancerawareness.org/CanineCancer-Hemangiosarcoma.html
http://www.peteducation.com
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