Two Ultra-Rare Primary Cardiovascular Sarcomas Characterized by 18F- FDG PET/CT: A Mini Case Series

Background: Primary cardiac and great vessel sarcomas are exceptionally rare malignancies that frequently mimic more common conditions such as pulmonary thromboembolism or benign cardiac tumors, often leading to delayed diagnosis. Case presentation: We report two instructive cases that highlight the pivotal role of 18F-FDG PET/CT in their identification. In the first case, a 54-year-old woman with chest pain was initially treated for pulmonary embolism. PET/CT revealed a hypermetabolic mass in the pulmonary trunk and right ventricular outflow tract (SUVmax 10.6) with multiple distant metastases. Targeted biopsy and the confirmation of MDM2 amplification by FISH established the diagnosis of pulmonary artery intimal sarcoma (stage IV). In the second case, a 23-year-old man with a history of atrial septal defect closure was found to have an incidental bi-atrial mass, which was considered typical for myxoma on echocardiography and CT. PET/CT, however, demonstrated heterogeneous but intense radiotracer uptake (SUVmax 6.3 on early imaging, increasing to 7.0 on delayed imaging). The patient underwent surgical debulking; although the intraoperative frozen section was misinterpreted as myxoma, the final histology—supported by a high Ki-67 proliferation index (≈40%)—established the diagnosis of primary cardiac myxoid sarcoma. Conclusions: In both instances, 18F-FDG PET/CT served as the critical diagnostic turning point by uncovering the underlying malignancy when conventional imaging findings were equivocal, enabling accurate staging and guiding subsequent management. These cases underscore the indispensable value of metabolic imaging and confirmatory molecular testing in the evaluation of suspected intracardiac or intravascular masses.