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A 70-year-old man underwent cardiac magnetic resonance (CMR) after a left atrial mass was discovered on echocardiography. A mobile, 3 × 2.6 × 2.9-cm, T2-bright mass was present at the base of the left atrial appendage, abutting the opening of the left superior pulmonary vein. The mass was not visible either on pre-contrast T1-weighted dark-blood images or on pre-contrast steady-state free precession bright-blood images (Fig. 1). Serial post-contrast imaging revealed very gradual centripetal enhancement (Fig. 2). Because the imaging features were not typical for thrombus, the mass was believed to be a benign tumor, such as a myxoma.
The mass was excised. Intraoperative transesophageal echocardiography showed many important features of the mass (Fig. 3). On gross pathology, the mass was gelatinous and friable. Immunohistochemical staining led to the diagnosis of a very large papillary fibroelastoma, the 2nd most common benign primary tumor of the heart (after myxoma).1–4
Papillary fibroelastomas are usually small (<1 cm) and mobile and are frequently attached to valve leaflets, although they can be found on any endocardial surface. Their enhancement is typically most distinct on CMR, and they usually have a low T2 signal. The risk of embolization necessitates their prompt surgical removal after detection.4,5
Cardiac magnetic resonance is useful for delineating most of the important aspects of masses in or around the heart, including their size, site, and breadth of attachment. It can also delineate their mobility, functional significance, tissue characterization, and enhancement pattern (which usually distinguishes a tumor from thrombus). However, this case reveals 2 important pitfalls of CMR: even large lesions might be stealthy on some pulse sequences, and serial post-contrast imaging might be necessary to determine the presence or absence of enhancement. As a consequence, typical papillary fibroelastomas—as well as other small, mobile masses—might be missed on routine CMR.
Address for reprints: Michael K. Atalay, MD, PhD, Department of Diagnostic Imaging, Rhode Island Hospital, 593 Eddy St., Providence, RI 02903