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Cancer of the Heart
1
Nick A. Schroeder, DVM, DACVIM (Cardiology) and Lisa DiBernardi, DVM, DACVIM (Oncology),
DACVR (Radiation Oncology) 2
1 LeadER Animal Specialty Hospital, Cooper City, FL, USA
2 Gulf Coast Veterinary Specialists, Houston, TX, USA

Etiology/Pathophysiology Heart‐based tumors (HBTs) constitute approximately 5%
of cases of cardiac neoplasia in the dog and up to 3% in cats
Cardiac neoplasia in small animals is usually associated and are commonly identified as incidental findings. Most of
with pericardial effusion. Most of the time, rupture of a these are aortic body tumors (ABTs, chemodectoma or par­
cardiac tumor occurs which leads to hemopericardium aganglionoma). These tumors arise from chemoreceptor
and cardiac tamponade. In dogs, the majority of cases cells sensitive to blood oxygen and carbon dioxide tension.
are secondary to malignant hemangiosarcoma. Cats Most ABTs are locally invasive and up to 21% are malignant,
most commonly have cardiac lymphoma. Diagnosis is metastasizing to lung, liver, left atrium, pericardium or
frequently based on echocardiographic location of the kidneys. Approximately 5–10% of all heart‐based tumors
mass lesion, taking into account the age and breed of the are ectopic thyroid carcinomas or parathyroid tumors.
animal, and only rarely is histopathologic confirmation These are rarely secretory or functional. Hemopericardium
achieved via surgical biopsy. Given the current rate may be present due to spontaneous hemorrhage from
of change in treatment modalities, consultation with a the mass itself. Alternatively, a hydropericardium with a
veterinary oncologist is recommended. modified transudate may develop secondary to obstruction
Tumors of the heart typically arise from the myocar­ of lymphatic drainage of the pericardial sac.
dium, the heart base or the pericardium and are com­ The myocardium may be infiltrated with neoplastic
monly associated with pericardial effusion. Pericardial lymphocytes (LSA), occasionally causing pericardial effu­
effusion is a relatively common condition in the dog, much sion, typically a modified transudate. Cardiac lymphoma
less so in the cat. Normally, there are only a few milliliters may be primary or multicentric.
of fluid present in the pericardial space, which serves Pericardial effusion may develop secondary to pericar­
to lubricate the epicardial surface. The pericardium is a dial mesothelioma. Pleural effusion may also occur in
tough, fibrous membrane. The purpose of the pericar­ affected animals with mesothelioma, often concomitant
dium is to stabilize the position of the heart within the with pericardial effusion.
thorax and provide some diastolic function. When signifi­ Other miscellaneous and rarely reported cardiac
cant amounts of fluid accumulate within the pericardial tumors include intrapericardial lipoma, rhabdomyosar­
space, cardiac function may be compromised, and affected coma, cardiac mxymoma, and other sarcomas.
animals may start to show clinical signs as described
below. The most common causes of pericardial effusion
are cardiac neoplasia and idiopathic pericardial effusion. Epidemiology
Malignant transformation of vascular endothelial cells
results in hemangiosarcoma (HSA). Cardiac HSA typi­ The prevalence of cardiac neoplasia in the dog has
cally arises from the tissue of the right atrium (RA) and/ been cited at 0.19% and is less than 0.03% in cats.
or right auricle (RAu), though other regions of the heart Primary cardiac neoplasia constitutes 84% of cases,
may occasionally be affected. Spontaneous hemorrhage with 16% representing metastatic lesions (most
causes hemopericardium. commonly hemangiosarcoma and adenocarcinoma).

Clinical Small Animal Internal Medicine Volume II, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical