Unusual Location for a Large Cardiac Fibroma
A 37-year-old woman with palpitations and chest discomfort was referred to our institution for assessment of a right ventricular (RV) mass seen on echocardiography (Figure 1). Cardiovascular magnetic resonance confirmed the presence of a large oval mass (6×7 cm) within the basal RV free wall (online-only Data Supplement Movies I and II). The mass was causing compression of the RV inlet but no invasion of the tricuspid annulus or valve (Figure 2). The mass had a low signal on T1- and T2-weighted images, no increase in signal during first-pass perfusion, but diffuse delayed hyperenhancement after gadolinium injection, with some central areas of relatively low signal (Figure 2, B through D). These features are typical of cardiac fibroma. On surgery, a large, lobulated solid mass was excised from the RV free wall (Figure 3). Histological analysis with hematoxylin-and-eosin staining showed dense whorled areas with bland spindle cells and cardiac myocytes at the edge (Figure 4A). Elastin–Van Gieson trichrome staining revealed a profusion of collagen admixed with elastin fibers (Figure 4B). The spindle cells were immunopositive for smooth muscle actin, which confirmed fibroma (Figure 4C).
Cardiac fibromas commonly present in infancy and adolescence and frequently involve the interventricular septum and left ventricular free wall. Involvement of the right side of the heart by fibromas is uncommon, and differential diagnoses include other primary benign tumors (such as myxoma, lipoma, rhabdomyoma, and hemangioma) and malignant tumors (such as sarcomas, lymphomas, and cardiac metastases). On magnetic resonance imaging, fibroma is the only intramural tumor to have a combination of an intermediate-low signal on T1-weighted images plus a low signal on T2-weighted images, which reflects small intracellular and vascular space and low water content. Myxomas can also have an intermediate signal on T1 and a low signal on T2 images, but they are intracavitary in nature. A lipoma has a typically high T1 signal due to high fat content. Cardiac rhabdomyomas are frequently multiple and return an intermediate-high signal on T1 and an intermediate signal on T2 images. Hemangiomas are enhanced with first-pass perfusion and have an increased signal on T2 images (probably because of slow-flowing blood in the tumor vessels). Finally, malignant tumors tend to return a high signal on T2-weighted images as a result of increased water content due to cellular necrosis and tissue inflammation. In addition to the characteristics described above, the other differentiating feature of cardiac fibromas is delayed hyperenhancement after gadolinium injection, which is usually more intense than with any other tumor. This feature reflects contrast accumulation within an expanded extracellular compartment by deposition of collagen and elastin fibers (Figures 2D and 4).
This work was supported by the NIHR Cardiovascular Biomedical Research Unit of Royal Brompton and Harefield NHS Foundation Trust and Imperial College London.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/lookup/suppl/doi:10.1161.CIRCULATIONAHA.111.018374/-/DC1.
- © 2011 American Heart Association, Inc.