Cardiac lipoma of the right atrial appendage: Multimodality imaging of a rare tumor at an uncommon site.

Cardiac lipomas are rare benign tumors that are often asymptomatic and discovered incidentally. While the right atrium is a recognized location for such tumors, involvement of the right atrial appendage (RAA) has not been previously reported. We describe a 60-year-old woman presenting with acute pulmonary embolism, during which a small, mobile, fat-containing mass in the RAA was incidentally discovered on computed tomography pulmonary angiography. Further characterization by cardiac magnetic resonance imaging confirmed features consistent with a lipoma. Although the lipoma was not directly implicated in the embolic event, which was the cause of the patient's symptoms, its mobility and location raised concerns for future complications. RAA involvement poses unique diagnostic and management challenges. Its narrow orifice often limits transthoracic echocardiography sensitivity, frequently requiring advanced multimodality imaging for detection. Furthermore, the relatively stagnant blood flow within the appendage, combined with a mobile mass, increases the theoretical risk of blood flow obstruction and secondary thrombus formation. Preoperative detection is critical, as the RAA is a common site for venous cannulation; its involvement requires modified surgical strategies to prevent accidental tumor dislodgement or impaired venous return. A multidisciplinary team recommended surgical resection, which was successfully performed via minimally invasive cardiac surgery. Histopathology confirmed a benign lipoma. This case highlights the diagnostic value of multimodality imaging in evaluating incidental cardiac masses, the importance of individualized risk assessment, and the unique procedural considerations posed by RAA involvement.