Cardiac neoplasia is very rare in cats. The most common types of cardiac neoplasias reported are hemangiosarcomas, chemodectomas, lymphomas, and ectopic thyroid carcinomas. In cats these neoplasms are usually primary, malignant and the majority are extranodal lymphomas. Most secondary/metastatic tumors are found in the left ventricular free wall and interventricular septum.

Patients with a cardiac mass can present with no clinical signs or they can present with signs of respiratory distress and decreased cardiac output, as well as  signs of right sided congestive heart failure related to pleural and pericardial effusions from the mass. Clinical signs include acute collapse, exercise intolerance, lethargy, weight loss, vomiting, syncopal episodes or sudden death. On physical examination there may be muffled heart sounds, tachycardia, pulse deficits, pale mucous membranes, weak femoral pulses, ascites, and tachypnea/dyspnea.

Cardiac neoplasms may be detected on radiographs but typically ultrasound is needed to confirm. An echocardiogram can determine location and size of mass and give some insight into the type of mass. Definitive diagnosis is challenging as cardiac masses are not routinely sampled due to the risk of arrhythmias and hemorrhage. More commonly a pleural or pericardial effusion is sampled to determine etiology. Necropsy and histopathology are utilized for definitive diagnosis post mortem.

Treatment in these cases is challenging as it is difficult to obtain a definitive diagnosis. Surgery, chemotherapy, radiation therapy, and supportive treatment such as pericardio/thoracocentesis can help extend life but in general the outcome is usually poor. In cats diagnosed with lymphoma, some are able to achieve remission using the CHOP protocol. ^{1 2 3}