¹⁸F-FDG PET/CT in left atrial undifferentiated pleomorphic sarcoma with osteosarcomatous differentiation

Primary cardiac sarcomas are rare and sometimes difficult to discern from benign tumors and intracardiac thrombi. We describe the ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/CT findings in a case of left atrial undifferentiated pleomorphic sarcoma with osteosarcomatous differentiation, presenting with severe mitral regurgitation and pulmonary hypertension. The tumor presented as a broad-base mass protruding into the cardiac lumen, accompanied by punctate calcification-like high attenuation on CT. ¹⁸F-FDG PET/CT revealed high ¹⁸F-FDG uptake in the mass. Severe mitral regurgitation, a rare manifestation, was caused by tumor extension to the mitral valve leaflets and subvalvular tissue, which was best visualized on transesophageal echocardiography. This case illustrates the importance of multimodal diagnostic approaches including ¹⁸F-FDG PET/CT, which can facilitate accurate diagnosis and timely initiation of curative treatment, ultimately saving the patient's life.

Firstly, cardiac sarcomas, particularly those with calcification/ossification, are rare and may mimic benign tumors and chronic intracardiac thrombi. Multimodal imaging approach, including ¹⁸F-FDG PET/CT, may be helpful in the accurate diagnosis of malignancies. Second, left atrial undifferentiated pleomorphic sarcoma has the potential to extensively spread along the endocardium and can extend to involve the valve leaflets, resulting in mitral regurgitation and pulmonary hypertension.