Late-Stage Löffler's Endocarditis Mimicking Cardiac Tumor: A Case Report

Figure 1. Electrocardiogram reveals sinus rhythm and ST segment depression with T-wave inversion in leads V1-6.

Figure 2. (A) Transthoracic echocardiography in apical 5-chamber view reveals an echo-dense mass (30 × 39 mm, arrow) attached to the mid-anteroseptal wall of the left ventricle, extending to the anterolateral papillary muscle. (B) Color Doppler echocardiography in apical 3-chamber view reveals a cardiac mass (arrow), and entrapment of the anterolateral papillary muscle (arrowheads), causing moderate mitral regurgitation. Ao, Aorta; LA, Left atrium; LV, Left ventricle; RV, Right ventricle.

Figure 3. (A) Contrast-enhanced computed tomography scan at early phase reveals an irregular cardiac mass attached to the left ventricle in several locations (arrow). (B) Note the reduced mass with a delayed contrast enhancement at late phase (arrow). (C) Axial dynamic cardiac magnetic resonance imaging reveals a low echogenic left ventricular mass attached to the anteroseptal and inferior walls, and the anterolateral papillary muscle (arrows). (D) Late gadolinium enhancement image reveals subendocardial enhancement in anteroseptal and inferior walls, mid-wall enhancement in lateral wall, and heterogeneous enhancement within the cardiac mass and the adjacent anterolateral papillary muscle (arrowheads). LA, Left atrium; LAA, Left atrial appendage; LV, Left ventricle; pm, Papillary muscle; RV, Right ventricle.

Figure 4. (A–D) Photomicrograph of the resected mass. (A) Low-power view with Masson trichrome stain reveals endocardial fibrosis and intracardiac thrombosis at various stages. Note the mixed thrombus consisting of well-organized thrombus (asterisk) and fresh thrombus (double asterisk). En, Endocardium; My, Myocardium; Th, Thrombus; Bars: 1 mm. (B) A high-power view reveals proliferating neovascularization (black arrows) with inflammatory infiltrates in the border zone of endocardial fibrosis and mural thrombus (magnified view around white arrow in A). Bars: 20 μm. (C) A high-power view with hematoxylin-eosin stain reveals focal eosinophilic infiltrate in the endocardium. Bars: 20 μm. (D) Immunostaining with an antibody against the major basic protein. Bars: 20 μm.

Figure 5. Timeline of the case. ALPM, Anterolateral papillary muscle; Ao, Aorta; Echo, Echocardiography; ECG, Electrocardiogram; En, Endocardium; LGE, Late gadolinium enhancement; LV, Left ventricle; MR, Mitral regurgitation; My, Myocardium; pm, Papillary muscle; RV, Right ventricle; Th, Thrombus. The asterisk denotes well-organized thrombus, and double asterisk denotes fresh thrombus.

Figure 6. Red flags that should be highly suspected of Löffler's endocarditis. ECG, Electrocardiogram; Echo, Echocardiography; 3DSTE, Three-dimensional speckle tracking echocardiography; LA, Left atrium; RA, Right atrium; GLS, Global longitudinal strain; LV, Left ventricle; RV, Right ventricle; MV, mitral valve; AV, aortic valve.

Figure 7. Diagnostic algorithm for patients with suspected Löffler's endocarditis. LE, Löffler's endocarditis; –, negative test; +, positive test; CMR, Cardiovascular magnetic resonance; SSFP, Steady-state free precession; T2WI, T2-weighted imaging; LGE, Late gadolinium enhancement; FTA, Feature-tracking based strain analysis; IHC, Immunohistochemistry; EM, Electron microscopy; ECG, Electrocardiogram; Echo, Echocardiography.