Page 810 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

788 PART IV Specific Malignancies in the Small Animal Patient

be benign or malignant, with the latter predominating, and most Diagnostic Techniques and Workup
occur in the right atrium and auricle in the dog. 323,329 Cardiac Differential diagnosis of a cardiac tumor is often made based on
HSA is frequently associated with hemorrhagic pericardial effu-
VetBooks.ir sion and cardiac tamponade and tends to have high rates of clinical history, physical examination, and radiographic find-
ABTs are the second most common pri-
ings. Diagnosis requires imaging, which is routinely achieved by
metastasis.
330,332,347
mary neoplasm of the heart in dogs, and lymphoma and ecto- echocardiography and sometimes through additional advanced
pic thyroid carcinoma are observed with some frequency as modalities such as CT or MRI. Incidental diagnosis of subclinical
well. 323–326,329,348–359 Reported but rare malignant tumors include cardiac tumors may be encountered at necropsy. In the major-
mesothelioma, myxosarcoma, chondrosarcoma, fibrosarcoma, ity of cases, antemortem cytologic or histologic confirmation of
osteosarcoma, rhabdomyosarcoma, undifferentiated sarcoma, neoplasia is not obtained; however, in cases where technically fea-
leiomyosarcoma, thyroid carcinosarcoma, peripheral nerve sheath sible and with acceptable clinical risk, FNA or biopsy may provide
tumor, granular cell tumor, malignant mesenchymoma, and ana- importance guidance on therapeutic options. 422
plastic carcinoma. 360–385 Histologically benign cardiac tumors Much like clinical signs, physical exam findings vary widely
have been reported and may cause lifethreatening clinical signs depending on location and hemodynamic consequences of the
because of their location despite their biologically benign behav- cardiac tumor. Patients with incidentally identified cardiac tumors
ior. Reported benign cardiac tumors include myxoma, lipoma, may have apparently normal physical examinations. Auscultatory
thyroid adenoma, hamartoma, Schwannoma, leiomyoma, and abnormalities are common secondary to pericardial effusion and
fibroma. 359,386–399 In contrast to those in humans, metastatic include muffled heart sounds, pericardial friction rubs, or tumor
cardiac tumors are diagnosed with less frequency than primary plops (intermittent diastolic sounds secondary to tumor motion).
tumors in dogs, likely due to the high incidence of cardiac HSA In addition, arrhythmias may be auscultated, particularly in
in this species and absence of cardiac specific clinical signs for patients with myocardial involvement. Pulmonary auscultation
many secondary tumors. 323,326,328 Tumors reported to metastasize may reveal abnormalities consistent with left-sided congestive
to the heart in dogs include HSA, lymphoma, mammary gland heart failure, such as increased bronchovesicular sounds and/or
carcinoma, melanoma, pheochromocytoma, histiocytic sarcoma, soft crackles. Pulse quality derangements are common in patients
gastric adenocarcinoma, liposarcoma, malignant mesenchymoma, in low-output states, such as cardiac tamponade. Jugular venous
rhabdomyosarcoma, extraskeletal osteosarcoma, fibrosarcoma, distention and pulsation may also be observed secondary to ele-
and pulmonary carcinoma. 326,328,400–412 vated right heart pressure with pericardial effusion or obstructive
Cardiac tumors in cats tend to be malignant although benign lesions.
intrapericardial cysts have been reported. 413,414 In addition to lym- Many components of the diagnostic evaluation are related
phoma, ABT, and HSA, single case reports of primary cardiac ganglio- to the common concomitant condition of pericardial effusion.
neuroma, rhabdomyosarcoma, and myxoma exist. 415–417 Metastatic An electrocardiogram may be normal in patients with cardiac
lesions have been reported to arise from squamous cell carcinoma, tumors or may show a wide variety of cardiac arrhythmias,
mammary gland carcinoma, and pulmonary carcinoma. 326,418 which are frequently related to the site of the cardiac tumor and
infiltration of the myocardium. 423 Conduction disturbances,
History and Clinical Signs such as atrioventricular blocks or bundle branch blocks, may
be observed with myocardial infiltration and may be as severe
Tumors of the heart generally cause clinical signs secondary as complete atrioventricular block as previously reported with
to alterations of cardiac function and may result from a mass cardiac lymphoma. 349 Supraventricular or ventricular arrhyth-
obstructing blood flow to and from the heart, external cardiac mias may be observed in cases of cardiac tumors with or without
compression that impedes filling such as pericardial effusion, and/ pericardial effusion. ST segment changes may be observed sec-
or arrhythmias or decreased contractility resulting from myocar- ondary to myocardial ischemia with or without pericardial effu-
dial infiltration or ischemia of the myocardium. Clinical signs are sion. 424 Sinus tachycardia is common with cardiac tamponade
influenced more by the tumor location, tumor size, and presence or in cases with heart failure acquired secondary to obstructive
of pericardial effusion than the specific histology of the tumor. cardiac tumors.
Sudden death may occur secondary to cardiac arrhythmias or
tumor rupture and subsequent blood loss, with or without car-
diac tamponade. Tumors, particularly cardiac HSA, arising in the
right side of the heart often cause signs of right-sided congestive
heart failure due to inflow obstruction or the presence of cardiac TABLE 34.3 Frequency of Commonly Reported
tamponade secondary to pericardial effusion. Signs of right heart Clinical Signs for Dogs with Suspected or
failure often result from the presence of bi- or tricavitary effusion Confirmed Cardiac Hemangiosarcoma
and may present as abdominal distention, dyspnea, exercise intol- Reported Frequency
erance, and/or acute collapse. Clinical signs commonly reported Clinical Sign (%) 331,332,458,459,462
for dogs with confirmed or suspected HSA of the heart are often
nonspecific in nature and are described in Table 34.3. Lethargy 35–93
Clinical signs associated with ABT may include abdominal dis- Anorexia or inappetence 19–46
tension, weight loss, dyspnea, anorexia or inappetence, signs of gas-
trointestinal tract disease, lethargy, cough, and collapse. Although Acute collapse 13–54
many dogs with ABT may have clinical signs that persist for weeks to Coughing/respiratory difficulty 13–42
months before diagnosis, some will present acutely as well. 336,419,420
Clinical signs for cats with cardiac neoplasia most frequently include Vomiting 11–38
tachypnea, dyspnea, hyporexia, weight loss, and lethargy; acute col- Weakness 0–56
lapse appears to occur less frequently than in dogs. 339,345,421