The commonest intracavitary benign cardiac tumour is

Myxoma, a benign tumor, is the most common type of primary cardiac tumor. Cardiac tumors may occur in any cardiac tissue. They can cause valvular or inflow-outflow tract obstruction, thromboembolism, arrhythmias, or pericardial disorders. Diagnosis is by echocardiography and frequently cardiac MRI. Ref Davidson 23rd edition pg 455