Pathologic quiz case: a symptomatic right atrial mass. Papillary fibroelastoma.

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A woman with a history of hypertension presented with acute onset of diplopia, which rapidly progressed to right facial and upper extremity paresthesia and weakness. The patient denied chest pain, shortness of breath, palpitations, or nausea. All vital signs were within normal limits, and no precordial murmurs, friction rubs, or thrills were present. An electrocardiogram showed normal sinus rhythm. Computed tomographic scan of the head was negative, a magnetic resonance image showed only mild small vessel ischemic changes in the brain, and a bilateral carotid Doppler examination was normal. Transthoracic echocardiogram revealed a heart of normal size, an ejection fraction of 60%, and a 1.5-cm right atrial mass that did not obstruct the tricuspid valve. Tricuspid regurgitation was not present. The patient’s symptoms resolved completely within 18 hours of presentation. Further workup via a transesophageal echocardiogram showed a 2-cm right atrial mass (Figure 1, small arrowhead), which was arising directly from the tricuspid valve (Figure 1, large arrowhead). The patient underwent an open-heart resection of this mass. Gross examination of the specimen revealed multiple fragments of a tan-yellow papillary mass measuring 3.2 3 2.8 3 1.4 cm in aggregate. Flotation of the mass in saline was reminiscent of a ‘‘sea anemone’’ with frondlike projections. Microscopic examination delineated a papillary structure with avascular cores composed of a hyalinized and focally myxoid stroma with scattered stellate fibroblasts (Figure 2). The papillary structures were lined by a simple, flattened endothelial lining in continuity with the normal valvular endothelium. An elastin stain of the papillae demonstrated a central, loosely lamellated elastic tissue core with tapering rudimentary elastin fibers located toward the periphery (Figure 3). What is your diagnosis?