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CANINE
HEMANGIOPERICYTOMA
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THE
PET HEALTH LIBRARY
Hemangiopericytoma
Hemangiopericytoma is a common
tumor in dogs, generally arising on the limbs and appearing as a round
nodule. It derives from pericytes (see below) associated with blood vessels
and, at least in some cases, involves a chromosome abnormality, usually
an extra or an absent chromosome. Hemangiopericytomas are often bald, pigmented,
or even ulcerated.
What Is a Pericyte?
Consider that everyone began life as a single cell. This cell divided
over and over and became many cells. Finally we became groups of different
types of cells. Eventually we became embryos, fetuses, and finally infants
with complete organ systems and different tissues all derived from one original
cell. During the course of this amazing development, some cells do not
specialize fully into specific tissues. They stay "undifferentiated" and
can in the future specialize into whatever type of cell our body might require
at that time. We have cells throughout our bodies that simply "stayed put"
at different stages of embryonic development. Pericytes are such cells.
A pathology instructor once described the pericyte as perhaps not the Adam
and Eve of our bodies but more like Abraham.
What Is a Hemangiopericytoma?
A hemangiopericytoma is a tumor arising from pericytes associated with
blood vessels. It appears that these pericytes have chromosomal abnormalities
from improper cell division and this ultimately leads to their division
into a tumor instead of some more useful tissue.
Is it Cancer?
The hemangiopericytoma does not spread through the body in the way one
normally thinks of cancer. It does, however, tend to recur at the site
where it was originally removed. When it recurs, it tends to grow back
more deeply rooted and more difficult to remove than it was in its original
form. If left alone, it will continue to grow inexorably over usually years
until it invades a part of the body that does not have extra space to allow
a tumor (usually the chest cavity is the closest such area.)
If left alone, this tumor eventually becomes inoperable, disfiguring,
and lethal though generally this takes years.
What are the Treatment Options?
Radiation therapy
The hemangiopericytoma is responsive to radiation therapy. This means
that the cure rate after radiotherapy is 80% to 90%. Only the tumor
site receives radiation in this type of therapy so the patient does not become
ill, though the area of radiation exposure will probably lose the ability
to grow hair. Effective radiation therapy unfortunately requires 15 to 18
treatments. For radiotherapy to be effective, the tumor must first be surgically
removed without any visible remaining tumor present; otherwise the tumor
is will be too big to respond.
Leave the tumor alone for now and attempt another surgical removal when
it recurs.
One option is to wait and see if the tumor regrows (it usually does).
When it regrows, it can be removed again; however, when it re-grows, it is
usually more difficult to remove. Every time it is removed, it re-grows more
invasively, making the next surgery more difficult. If a second surgery removes
the visible portions of the tumor successfully, radiation therapy can again
be considered as above with similar success rate.
Leave the tumor alone and allow it to recur without treatment.
This may be a realistic option for an elderly patient as the hemangiopericytoma
typically requires 6 to 12 months to grow back and longer to become disfiguring
or invasive. For a younger patient, this is probably a poor option as the
tumor will eventually become, as mentioned, inoperable, disfiguring, and
lethal.
Allow the tumor to recur then amputate the limb.
This may seem extreme but it certainly resolves the lethal aspect of
the tumor in a curative manner. The hemangiopericytoma does not spread
distantly in the body so amputation of the limb achieves cure and does
so far less expensively than radiotherapy.
Copyright
2003 - 2007 by the Veterinary Information Network, Inc. All rights reserved.
This work was originally published by Veterinary
Information Network, Inc. (VIN)
and is republished with VIN's permission.
The above information is simply informational.
It's intent is not to replace the advice of a veterinarian nor to assist
you in making a diagnosis of your pet. Please consult with your own veterinarian
for confirmation of any diagnosis. Your pets life may depend on it.
