The Role of Cardiac MRI in Diagnosing Rare Intracardiac Metastasis from Non-Clear Cell Renal Cell Carcinoma: A Case Report (QF_TH_002)

Description of Clinical Presentation: Renal cell carcinoma (RCC) metastasizes predominantly to the lungs, bones, and liver, while cardiac metastasis is exceedingly rare, especially in the case of non-clear cell RCC. Intracardiac involvement, particularly affecting the right ventricle, presents a diagnostic challenge. Cardiac MRI, with its superior tissue characterization capabilities, provides detailed insights into such rare cases. We present a case of a 55-year-old male with a history of non-clear cell RCC who presented with progressive dyspnea and fatigue. Transthoracic echocardiography revealed a right ventricular mass. Further evaluation with cardiac MRI confirmed the presence of a heterogeneously enhancing mass within the right ventricle, with tissue characteristics consistent with metastatic disease.

Diagnostic Techniques and Their Most Important Findings: Transthoracic Echocardiography (TTE) demonstrated a large mass within the right ventricle, attached to the right ventricular free wall, measuring approximately 2.1 x 2.3 cm. The mass was mobile and extended towards the tricuspid valve during diastole, causing moderate obstruction of the right ventricular inflow. Cardiac MRI was performed for further characterization of the mass, and the following findings were observed:
T1-Weighted Imaging: The mass appeared isointense relative to the myocardium, with areas of hyperintensity suggestive of hemorrhagic components.
T2-Weighted Imaging: The mass showed heterogeneous hyperintensity, consistent with necrosis and cystic degeneration.
Cine MRI: The mass was observed to have significant mobility, extending towards the tricuspid valve and causing intermittent obstruction, correlating with the patient’s symptoms of dyspnea.
Post-contrast Enhancement (Gadolinium): The mass showed heterogeneous gadolinium enhancement, indicative of its vascularity, which is characteristic of metastatic tumors.
Late Gadolinium Enhancement (LGE): The mass exhibited areas of delayed enhancement, reflecting fibrotic and necrotic tissue, further supporting its malignant nature.
The MRI findings strongly suggested a metastatic tumor rather than a thrombus, given its enhancement pattern, tissue heterogeneity, and vascularity.

Learning Points from this Case: Intracardiac metastasis from renal cell carcinoma, although rare, poses significant diagnostic challenges. While transthoracic echocardiography is often the first imaging modality used, it lacks the tissue characterization capabilities necessary for a definitive diagnosis. Cardiac MRI is invaluable in such cases, allowing for a detailed assessment of the mass’s size, location, mobility, and tissue characteristics. 
In this case, the combination of T1- and T2-weighted images, along with contrast-enhanced sequences, helped identify the vascular nature of the tumor, distinguish it from benign lesions like thrombi, and characterize necrotic and hemorrhagic areas. The heterogeneity of signal intensities and post-contrast enhancement are hallmarks of malignant cardiac masses, which guided the clinicians towards a metastatic origin.