Hemangiosarcomas are a form of
cancer which originates in the endothelium, which is the lining of blood
vessels and spleen. As might be expected of a tumor arising in the blood
system they are highly malignant and can be found almost anywhere in the
body since blood vessels are necessary in almost all body tissues. There
is a strong predilection for the spleen, pericardium and heart. These tumors
are most common in middle aged or older dogs which are medium sized or larger
but can occur in any breed. German shepherds are reported to be more susceptible
to this tumor than most dog breeds. In our practice golden retrievers also
seem to have a higher than normal incidence.
Because these tumors arise in internal organs there is often little warning
that they are present prior to time they cause severe clinical signs of disease.
A common estimate of the average time from discovery of the tumor until death
occurs in affected dogs is six to eight weeks but death occurs more rapidly
than this in a number of cases.
Visible bleeding, usually in the form of nosebleeds, and signs associated
with blood loss, such as tiring easily, episodes of unexplained weakness,
pale color to the mucous membranes of the mouth and eyes, increased respiratory
rates, abdominal swelling and depression are the most common presenting signs
for patients with hemangiosarcoma. A few dogs just suddenly die with no clinical
signs having been noted by their families prior to death. Bleeding disorders
associated with hemangiosarcoma are sometimes confused with immune mediated
hemolytic anemia (IMHA) because the type of anemia caused by the two conditions
is very similar and early clinical signs are often very similar, as well.
Hemangiosarcomas can cause very large tumors, sometimes as large as ten or
more pounds, when they affect the spleen.
In most instances tumors of this size in this location are found on physical
exam. In other cases the tumor affects the heart and is hard to find on a
physical exam and even easy to miss or X-rays. Sometimes there are hundreds
of small tumors spread throughout the body and surgical exploration or an
autopsy are the only ways to identify the problem.
The blood disorder that most commonly accompanies the presence of hemangiosarcoma
tumors is disseminated intravascular coagulation (DIC). This is blood clotting
that is occurring inappropriately inside the blood vessels. It uses up all
of the blood clotting elements rapidly and dogs with this condition usually
have platelet deficiencies, increased blood clotting times, decrease in fibrin
content in the blood and an increase in fibrin degradation products (FDPs).
This is probably the cause of death in most dogs affected with hemangiosarcoma.
Diagnosis of hemangiosarcoma can be accomplished in a number of ways. Identification
of a tumor in the spleen or heart raises a high degree of suspicion for this
tumor. Abdominal swelling is also highly suggestive in an older large breed
dog. If fluid is aspirated from the abdomen and it looks like blood it is
even more suggestive of hemangiosarcoma. If blood is drawn and will not clot
when left in the syringe it is another sign that a dog may have this tumor.
In some cases careful evaluation of the type of bleeding disorder present
is necessary to raise the suspicion of hemangiosarcoma.
If a tumor is identified when it is small it may be possible to remove the
spleen if the tumor is there or even to remove tumors found near the heart
and prolong the pet's life. Most of the time this will not make much difference,
though. These are highly malignant tumors and most have spread by the time
they can be identified. To the best of my knowledge there is not a very successful
hemotherapeutic or radiation protocol for this cancer at this time but dogs
treated with chemotherapeutic agents do live a little longer than dogs that
do not receive this treatment.
Treatment for the bleeding disorders and aggressive supportive care also
prolong the life of patients with hemangiosarcoma. If treatment for IMHA
or immune mediated thrombocytopenia (ITP) are instituted due to confusion
over the underlying cause of clinical signs early in the diagnostic process
there is not likely to be any harm to the dog.
Due to the tendency to look for an inciting agent in IMHA and ITP it is a
good idea to consider an autopsy exam if a dog dies before a definite diagnosis
of any of these conditions can be made. Finding hemangiosarcoma saves a lot
of agonizing over possible causes of the death of a friend. There are no
known predisposing factors other than size and breed that I am aware of for
hemangiosarcoma.
