**Introduction/Hypothesis:**
Papillary fibroelastomas (PFEs) are the most common primary benign cardiac tumors, often involving valvular surfaces. However, they can occasionally be found in atypical locations such as the left atrium, where they may mimic cardiac myxomas (CM). This case aims to illustrate the diagnostic challenges when a PFE presents with clinical and imaging features suggestive of a myxoma.

**Methods**
We describe an interesting case of pathology-proven PFE mimicking a cardiac myxoma. Patient data, including demographics and mass characteristics, clinical presentation, diagnostic imaging, and histopathologic evaluations are described.

**Results**
A 66-year-old female with a medical history notable for paroxysmal atrial fibrillation and two cerebrovascular accidents (CVA) in the last 10 years presented with new complaints of fatigue, shortness of breath, and dizziness on exertion for the past few months. Her first stroke occurred in 2014, during which she experienced dizziness, and a brain MRI revealed acute diffusion restriction in the right cerebellum. The second stroke, in 2015, presented with dizziness, aphasia, and right arm numbness, with an MRI showing multiple small infarcts in the left cerebral hemisphere, including the frontal, parietal and temporal lobes, likely of embolic origin. Following her last stroke, she was prescribed coumadin for anticoagulation after continuous telemetry detected atrial fibrillation. Since starting anticoagulation therapy, she did not experience any cerebrovascular symptoms.
The patient underwent a transthoracic echocardiogram (TTE) revealing a 21x15mm echodensity in the left atrium. Transesophageal echocardiogram (TEE) 2 weeks later confirmed the findings.  The mass had a heterogenous appearance and an irregular border. It appeared to be attached to the left atrial wall above the posterior mitral valve leaflet, findings suggestive of a myxoma.
Following discussion with multidisciplinary team and given her history of multiple CVAs and current symptoms, open surgical resection of the mass was performed, surprisingly yielding a 23 x 22 mm mass with numerous papillary fronds on gross pathological examination. Histologically, the papillary fronds were thin and branching (Hematoxylin & Eosin, 2x). The cores were comprised of mostly collagen fibrosis and elastic tissue, highlighted by the elastin stain (Verhoeff-Van Gieson stain, 2X). Focally, the papillary fronds were collapsed and predominantly myxoid, consistent with a PFE. Consequently, a calretinin immunostain (inset), which is used to identify myxoma cells, was performed to ensure the diagnosis and yielded a negative result.

**Conclusion**
Despite their rarity, PFEs should be considered in patients presenting with left atrial masses, even if the clinical presentation is atypical. Accurate histopathological diagnosis is crucial for proper management and improving patient outcomes.  This case points out that although PFE is most commonly found on cardiac valves, they can present on any endocardial surface, and even masquerade as a myxoma. The treatment in this case is justifiably surgical.



A Rare Case of Left Atrial Papillary Fibroelastoma mimicking a Myxoma 

This course will explore basic and cutting-edge imaging techniques to improve patient care and hone individual skills in performance and interpretation of echocardiography, nuclear cardiology, cardiac computed tomography, and cardiovascular magnetic resonance imaging. Days will reinforce how cardiovascular imaging may improve comprehension in ischemic heart disease, structural heart disease, cardiomyopathies, and heart failure. Experts will utilize novel techniques to reinforce key topics including taped interventional cases and a strong emphasis on case presentations.