Cardiac mucinous neoplasm is the most common primary tumor of the heart in clinical practice, mostly benign and rarely malignant. Mucinous tumors can occur in the endocardial surface of all hearts, 95% in the atria, about 75% in the left atrium, 20% in the right atrium, and 2.5% in the left and right ventricles. Mucinous tumors in the left atrium often occur near the fossa ovalis. Clinically, the tumor often blocks the mitral valve orifice, resulting in stenosis or incomplete closure of the mitral valve orifice. Mucinous tumors can occur at any age, but are most common in middle age and are more common in women. The clinical manifestations of this disease depend on the location, size, nature of the tumor, and the presence or absence and length of the tip. If the tumor is large and the tip is long, it may cause atrioventricular valve stenosis or incomplete closure, which may lead to hemodynamic changes and a series of symptoms, while if the tumor is small and the tip is short, it may be asymptomatic for a long time. (If the left atrial mucinous tumor obstructs the pulmonary vein or mitral valve orifice, it may produce symptoms of pulmonary stasis similar to mitral valve lesions; paroxysmal nocturnal dyspnea, hematochezia, jugular vein anger, hepatomegaly and swelling of lower limbs in severe cases. Right atrial mucinous tumors that obstruct the vena cava and tricuspid valve orifice may present with symptoms similar to those of pericardial effusion; jugular venous irritation, hepatomegaly, and edema. The obstructive symptoms of this disease are characterized by episodes with position changes, such as position-related episodes of vertigo and dyspnea, and sudden fainting or cardiac arrest may occur when the tumor suddenly blocks the atrioventricular valve orifice causing a significant decrease in the heart beat volume. (B) Embolization of mucinous tumor fragments or thrombus dislodged from the surface of the tumor can lead to embolization of the body and pulmonary circulation. Embolism occurs in about 40% of left atrial mucinous tumors and is rare in right atrial mucinous tumors. (c) Systemic symptoms include fever, increased sedimentation, anemia, weight loss and abnormal increase of serum α2 and β globulin, which may be related to hemorrhagic necrosis and inflammatory cell infiltration in the tumor.