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J Thorac Cardiovasc Surg 1997;114:672-674
© 1997 Mosby, Inc.

BRIEF COMMUNICATIONS

EXTRACARDIAC MYXOMA: AN UNUSUAL RIGHT VENTRICULAR EPICARDIAL LOCATION

Milan, Italy

Received for publication Jan. 6, 1997 accepted for publication Feb. 18, 1997. Address for reprints: Rita Spirito, MD, Department of Cardiac Surgery, University of Milan, Centro Cardiologico, fondazione I Monzino IRCCS, Via Parea, 4, 20138, Milano, Italy.

Cardiac myxoma is the most common heart neoplasm in adults, comprising about 50% of all primary cardiac tumors. ¹ This neoplasm is most prevalent between the third and the sixth decades of life, ² with women predominating. It can be associated with skin myxoma, mucocutaneous pigmentation, myxoid mammary fibroadenomatous neoplasms, and endocrine neoplasms. ¹ Farah ³ reported that this tumor seemed to be frequent in family members, suggesting an autosomal dominant mode of inheritance. Cardiac myxoma may be found in all cardiac chambers and on any of the heart valves. It is usually single but may be multiple. Myxomas occur three times more often in the left atrium than in the right and much less frequently in the ventricle. ^1-6 Of those rare ventricular myxomas, fewer than 5% develop in the right ventricle. ^1,6 In general, myxomas are round, polypoid, sessile, or pedunculated, and they vary in size from 1 to 15 cm in diameter. Histologically, the neoplasms consist of a basophilic mucoid matrix populated by groups of elongated spindle cells. Syncytial multinucleate giant cells are often present. ¹ Myxomas seem to be similar to embryonic endocardial cushion tissue, which may be multipotential endocardial tissue.

Clinical summary.

A 56-year-old woman was admitted in October 1995 with a diagnosis of an anterior mediastinal mass, which had been detected on a routine chest x-ray film. An echocardiogram and computed tomographic scan suggested that the mass arose from the thymus. A thoracoscopic examination revealed that the mass was in an epicardial location, appearing to be connected to the anterior wall of the right ventricle. Subsequently the patient was admitted for surgical treatment. She was free of symptoms and her physical examination showed no abnormalities.

Results of electrocardiographic, biochemical, and hematologic studies were within normal limits. A transesophageal echocardiogram confirmed the presence of an intrapericardial anterior mediastinal mass compressing the right ventricular outflow tract, as detected by high transpulmonary flow. A computed tomogram revealed a spheroidal lesion, 6 to 7 cm in diameter, located in the anterior mediastinal space with left paramedian extension. The mass had the characteristics of solid tissue (Fig. 1).

View larger version (121K): [in this window] [in a new window]   Fig. 1. Computed tomographic scan demonstrating the anterior mediastinal mass. 1, Myxoma; 2, right ventricle; 3, aorta.

View larger version (108K): [in this window] [in a new window]   Fig. 2. Intraoperative view showing the large size of the epicardial myxoma arising from the right ventricular anterior wall. 1, Myxoma; 2, right ventricle; 3, pulmonary artery conus.

The postoperative echocardiogram showed normalization of transpulmonary flow. The patient was discharged on the seventh postoperative day receiving no medications. One year later she was free of symptoms and an echocardiogram showed no recurrence.

Discussion.

Myxomas usually arise from multipotential reserve cells in or around the fossa ovalis of the interatrial septum. ^1-6 They are more common in women than in men. ¹ This tumor appears to be a multilobulated polypoid mass, pedunculated, but with a wide base attachment. Chromosomal aberrations have been observed in normal hearts, confirming the neoplastic origin of myxomas. The familial role in the genesis of these tumors has been described. ^3,5 They may appear as peripheral tumors (cutaneous myxomas, mucocutaneous pigmentation, myxoid mammary fibroadenomas) and endocrine neoplasms.

The genetic transmission of cardiac myxomas seems to be an autosomal dominant mode of inheritance. The rate of recurrence of myxomas is less than 5%. Usually, recurrence is due to embolization, inadequate resection, intraoperative implantation, or transformation from benign to malignant lesions. To our knowledge, no cardiac myxoma arising by a pedicle from the anterior wall of the right ventricle, located inside the pericardium, has previously been reported.

After total excision of the mass, microscopic examination revealed that the tumor had the characteristics of a myxoma covered by epicardial cells. The histogenesis of cardiac myxoma is uncertain. ⁶ The immunohistochemical profile of this mass revealed endothelial antigens, vimentin, and smooth muscle–actin positive cells, suggesting a neoplastic origin of the myxoma from endothelial and mesenchymal cells. These multipotential cells in a subepicardial location could differentiate into several cell types, including endothelial cells, fibrocytes, and smooth muscle cells.

Footnotes

From the Department of Cardiac Surgery^a and the Department of Pathology and Anatomy, University of Milan, Milan, Italy.

References

1. Chitwood WR Jr. Cardiac neoplasm: current diagnosis, pathology, and therapy. J Card Surg 1988;3:119-54. [Medline]
   
2. Wold LE, Lie JT. Cardiac myxoma: a clinicopathologic profile. Am J Pathol 1980;101:219-33. [Medline]
   
3. Farah MG. Familial cardiac myxoma: a study of relatives of patients with myxoma. Chest 1994;105:65-8. [Abstract/Free Full Text]
   
4. Viswanathan B, Luber JM, Bell-Thomson J. Right ventricular myxoma. Ann Thorac Surg 1985;39:280-1. [Abstract]
   
5. Heath D. Pathology of cardiac tumors. Am J Cardiol 1968;21:315-27. [Medline]
   
6. Burke AP, Virmani R. Cardiac myxoma: a clinicopathologic study. Am J Clin Pathol 1993;100:671-80.[Medline]
   

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