Essential Role of Multimodality Imaging in the Diagnosis of a Rare High-Grade Primary Cardiac Intimal Sarcoma

Background Primary cardiac intimal sarcoma is an exceptionally rare and aggressive malignant tumor that often mimics benign cardiac lesions, particularly atrial myxoma. Accurate diagnosis requires multimodality imaging and histopathological confirmation. Case Summary A 58-year-old woman presented with palpitations, exertional dyspnea, and recurrent syncope. Echocardiography and CT revealed a large, polypoid left atrial mass attached to the interatrial septum, initially suggestive of atrial myxoma. Due to hemodynamic compromise, urgent surgical resection was performed. Histopathology demonstrated a high-grade intimal sarcoma with myxoid stroma and MDM2 gene amplification. Initial staging showed no metastases; however, tumor recurrence in the left atrium occurred within two months. Cardiac MRI confirmed recurrent disease with delayed enhancement. Despite chemotherapy and subsequent radiotherapy for brain metastases, the tumor progressed, and the patient died seven months after diagnosis. Discussion This case highlights the diagnostic challenge of distinguishing benign from malignant cardiac tumors when echocardiography and computed tomography are used in isolation. Although echocardiography is the first-line modality for detecting cardiac masses, it provides limited tissue characterization, and CT offers limited soft-tissue contrast with nonspecific enhancement patterns. In contrast, cardiac magnetic resonance imaging provides superior soft-tissue resolution and multiparametric tissue characterization, allowing identification of heterogeneous signal intensity, necrosis, and infiltrative margins that favor malignancy. In this case, CMR findings supported the diagnosis of intimal sarcoma rather than myxoma. Given the aggressive biology and poor prognosis of intimal sarcoma despite multimodal therapy, early multidisciplinary evaluation in a specialized cardio-oncology center is essential.