In dogs haemangiosarcoma is the most common primary cardiac neoplasm and it usually affects
the right atrium. They may also be secondary having spread from another site. The
German shepherd dog may be predisposed to develop this type of tumour.
Heart base tumours (chemodectomas) are most commonly found in brachycephalic dogs
such as the boxer and Boston terrier (6-14 years of age) and males may be affected
more frequently. The tumours usually involve the aortic bodies lying at the base
of the aorta and pulmonary artery. They are often small and slow growing, but can
infiltrate locally. Ectopic thyroid or parathyroid tumours and lymphomas may also
occur at this site.
In cats primary cardiac tumours are rare. Haemangiosarcoma and lymphosarcoma are
the most common secondary metastatic neoplasms.
Depending upon the structures invaded or compressed by the growing tumour mass
a variety of clinical findings can be seen: