© Kirrawee Veterinary Hospital CANINE DISEASES
Mast cell tumor
Mast cell tumors are one of the more common skin tumors in dogs
and cats. They can vary in appearance from reddened crusty areas
to raised fleshy masses. Some mast cell tumors occur subcutaneously
(under the skin) and may be mistaken for lipomas (benign fat tumors).
Mast cells normally are involved in inflammatory reactions within
the body and they produce a number of substances which act on
blood vessels causing swelling, redness and sometime bruising.
These signs of inflammation may also occur around mast cell tumors
if the area is traumatized and in fact this feature may be used
to indicate a mass cell tumor using the Darier sign where a wheal
develops in response to the suspect area is pressed or scraped.
In dogs mast cell tumors are classified into three grades based
on the differentiation (normality of appearance) of the cells.
Grade 1 tumors have well differentiated cells and a low metastatic
potential (chance of spread) while grade 3 tumors are poorly differentiated
with a higher metastatic potential. It is difficult however to
define the degree of malignancy of mast cell tumors as they have
very individual and unpredictable behavior. Spread is usually
to local lymph nodes (draining glands) with spread to other organs
such as the lung being rare. Systemic spread (effecting the whole
body) is also possible in dogs where the tumor produces symptoms
of leukemia with cytopenias (raised white blood cells), generalized
depression and illness. Ulceration of the intestine with presence
of blood in the feces is a common secondary consequence of the
substances released from the mast cell tumors in dogs Cat with mast cell tumors tend to be middle-aged or older. The
cutaneous (skin) form usually develops as multiple, small raised
lesion primarily around the head and neck. Cats may also have
visceral (intestinal), and systemic forms of mast cell tumor.
The visceral tumors produce signs of vomiting and diarrhea, with
masses being palpable (able to be felt) in 50% of cases. The cutaneous
tumors in cats appear to be less aggressive than in dogs even
those which are poorly differentiated Mass cell tumors are treated where possible by wide surgical removal
(margins of 3cms). Radiation therapy can be used as a treatment
for areas where surgery cannot remove the required tissue. This
may be after partial removal of the tumor or as the sole treatment.
Radiation alone may be successful in up to 60% of patients. Chemotherapy
using prednisolone alone or in combination with other drugs such
as clophosphamide or chlorambucil can help to prolong the life
of animals with mast cell tumors which have already spread. They
will not however effect a cure of this condition. Cats have a
better prognosis (outlook) than dogs because of the less aggressive
nature of their tumors and generally will be cured with surgery
or radiation. Related sites |
