Left Ventricular Lipomatous Hamartoma Mimicking a Calcified Amorphous Tumor
A 56-year-old Japanese woman with type 1 diabetes mellitus for 20 years was referred for echocardiographic examination for a systolic ejection murmur. She had been undergoing hemodialysis for 10 years because of diabetic nephropathy, along with other diabetic complications, including proliferative retinopathy and neuropathy. She had a normal ECG, and her cardiothoracic ratio was 52% on chest x-ray. Laboratory examination showed poor control of blood sugar (casual blood glucose, 256 mg/dL; hemoglobin A1c, 9.3%) and renal dysfunction (blood urea nitrogen, 49 mg/dL [institutional normal range, 8–20 mg/dL]; creatinine, 8.5 mg/dL [institutional normal range for women, 0.4–0.9 mg/dL]), and her serum brain natriuretic peptide level was 48.4 pg/mL (institutional upper limit, 18.4 pg/mL). There was no evidence of infectious endocarditis.
Transthoracic echocardiography showed normal left ventricular (LV) size and normal systolic function with a slightly dilated left atrium. We found a mobile rod-like structure (5×20 mm) in the LV outflow tract (Figure 1A and Movie IA in the online-only Data Supplement), which had not been observed during a previous echocardiographic study 2 years previously (Figure 1B and Movie IB in the online-only Data Supplement). The base of the structure seemed to be adhered to the anterior side of the subaortic curtain and extended to the mitral annulus, which showed mitral annular calcification (Figure 1C and 1D and Movie IC and ID in the online-only Data Supplement). There was mild mitral regurgitation. Peak flow velocity of the LV outflow tract was 1.1 m/s (normal range, 0.8–1.4 m/s), and peak transaortic valve flow velocity was 2.1 m/s (normal range, 1.0–1.7 m/s), which was considered to be the cause of her heart murmur. A transesophageal echocardiographic image of the abnormal structure is shown in Figure 2 (Movie IIA–IIC in the online-only Data Supplement). The surface of the structure was smooth, and the internal echogenicity was uniformly very high. It was attached to the LV side of the mitral calcification. From the echocardiographic findings and clinical background, we suspected that the mass was a calcified amorphous tumor. Preoperative enhanced computed tomography provided no distinguishing features except mitral annular calcification.
Although she had neither symptoms of stroke nor abnormal findings on magnetic resonance imaging of the brain, we decided to perform a surgical resection because the risk of cardiogenic embolism by a large and mobile intracardiac mass was thought to be very high. As suggested by the echocardiographic examination, the mass was found to be attached to the LV outflow tract. It had the appearance of fat, being yellowish and relatively soft. The base was firmly attached to the calcified lesion of the aortic curtain. Surgical resection was performed successfully.
The resected mass was composed histologically of mature fat cells and small capillary vessels with no capsular tissues or calcified lesions (Figure 3). There were no neoplastic or inflamed areas. These findings suggested a possible diagnosis of lipomatous hamartoma.
Calcified amorphous tumors have been recognized since Reynolds et al1 reported 11 cases of nonneoplastic cardiac tumors characterized by a pedicle and diffuse calcification in patients with end-stage renal disease. They can originate in any of the 4 heart chambers and are usually associated with mitral annular calcification.2 Because the echocardiographic features of the mass in our patient were very similar to those described in previous reports,2 we provisionally diagnosed it as a calcified amorphous tumor before surgery.
Lipomatous lesions of the heart are very rare. On histology, they can be a lipoma, a fibrolipoma, a myolipoma, or an angiolipoma. All are well-circumscribed, encapsulated lesions, a feature that distinguishes them from lipomatous hamartomas, another type of rare, benign lipomatous cardiac tumor. To date, 6 cases of lipomatous hamartoma on the mitral valve, 4 on the tricuspid valve, and 1 on the aortic valve have been reported worldwide.3 The lipomatous hamartomas described in previous reports were multilobulated, yellowish, glistening lesions that had broad-based attachment to the valve leaflet. Our case is the first to be found growing rapidly in the LV outflow tract.
We thank Hiroaki Tada for providing us with previous echocardiograms of this patient.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/lookup/suppl/doi:10.1161/CIRCULATIONAHA.115.019252/-/DC1.
- © 2016 American Heart Association, Inc.
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