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Rhabdomyoma

(Tuberous Sclerosis)

A single large cardiac rhabdomyoma is seen involving the interventricular septum

Multiple cardiac rhabdomyomas are seen involving the ventricular septum and ventricular wall (arrows)

A large echogenic mass (arrows) representing a pericardial rhabdomyoma is seen.

Findings:

Three cases of differing patients all with cardiac rhabdomyomas. In each case the lesion is echogenic either involving the septum or ventricular wall.

 

Discussion:

The incidence of primary cardiac tumors varies between 0.0017 and 0.027% of all live births. Most are rhabdomyomas (60%), teratomas (20%) and fibromas (12%). Cardiac hemangiomas comprise about 2.8% of all primary cardiac tumors. In infants and children cardiac rhabdomyomas represent up to 90% of cardiac tumors. Myxomas have never been found in fetuses.

Primary cardiac tumors in infants are rare with an estimated prevalence of 0.01-0.05%. While the myxoma is the most common cardiac tumor for all age groups, the most common neonatal cardiac tumor is the rhabdomyoma, accounting for 58.3% of tumors. The remainder of cardiac tumors include teratomas (20%), fibromas (12%) and hemangiomas (3%). The in utero sonographic diagnosis of cardiac rhabdomyomas has been well documented. The typical appearance of the rhabdomyoma is an intracardiac echogenic mass, most commonly arising in either ventricle or from the interventricular septum. Detection of intracardiac masses is facilitated by routine inclusion of the four-chamber heart view.

Rhabdomyomas as described by Grebenc et al are "firm, white, well-circumscribed, lobulated nodules that occur in any location in the heart but are more common in the ventricles. They are myocardial (intramural) lesions. When multiple they can manifest as numerous miliary nodules measuring less than 1 mm in diameter ('rhabdomyomatosis').Cardiac rhabdomyomas may have detrimental effects on the fetus or newborn from a cardiovascular standpoint as there is a risk of arrhythmias, outflow tract obstruction, and non immune hydrops fetalis. Another potentially serious consequence is the high association of rhabdomyomas with tuberous sclerosis. Up to 50% of patients with a single cardiac rhabdomyoma have tuberous sclerosis and the incidence is even higher in patients with multiple rhabdomyomas. The incidence of tuberous sclerosis in fetuses with a prenatally diagnosed rhabdomyoma is unknown but may potentially be even higher.

Tuberous sclerosis or Bournevilleís disease is a neuroectodermal disorder characterized by the classic triad of mental retardation (71%), seizures (78%), and adenoma sebaceum (27%). Tuberous sclerosis predominantly consists of hamartomas occurring throughout the body in the brain, bones, skin, and viscera. Virtually all patients have brain involvement which may be identified in the neonatal period. Other sites of hamartomatous involvement include the kidneys (angiomyolipomas) and the heart (rhabdomyoma).

 

Obliqued transaxial and coronal images of the fetal head demonstrating the brightly echogenic tubers situated along the ventricular lining.

3mm single shot fast spin echo T2-weighted sagittal images. The hypointense lesions are the "tubers" situated along the ventricular lining (ependymal) and running from the ventricular surface out to the cortex (transmantle).

The syndrome is characterized by an autosomal dominant transmission with variable penetrance but also occurs as a result of a spontaneous mutation in up to 80% of cases. The gene for tuberous sclerosis is located on chromosome 9. Prognosis is variable depending on the degree of involvement with 30% mortality by age 5 and 75% mortality by age 20, usually due to central nervous system involvement. A definitive diagnosis of tuberous sclerosis as well as careful evaluation of other family members is thus imperative for genetic counseling.

Cardiac involvement in tuberous sclerosis is rare but is likely underestimated as many of the involved patients are infants and children in whom other changes of tuberous sclerosis have not yet become manifest. The prevalence of tuberous sclerosis has been shown to be higher in children (58%) than in adults (18%) demonstrating the regression of rhabdomyomas may occur spontaneously. Mortality has been reported to be even higher in tuberous sclerosis patients with cardiac involvement, reportedly up to 50% mortality during the first year of life and 90% mortality by puberty.

 

 

Multiple rhabdomyomas in an asymptomatic neonate

Sonograms from the mother's kidney and liver from the case of pericardial rhabdomyoma shown above. Angiomyolipomas and hamartomas are well seen (arrows).

As was mentioned above the differential diagnosis for a cardiac lesion includes: rhabdomyomas most commonly, as well as teratomas, fibromas and hemangiomas. The site as well as the sonographic appearance may help in this differential diagnosis.

 

A predominantly solid mass is seen within the thorax (arrow) associated with a large pericardial effusion. The mass was an intrapericardial teratoma.

 

References:

Gushiken BJ, Callen PW, Silverman NH. Prenatal diagnosis of tuberous sclerosis in monozygotic twins with cardiac masses. J Ultrasound Med 18:165-168, 1999

Choi JM, Jaffe R, Maidman J, Baxi LV. Multiple cardiac rhabdomyomas detected in utero. Fetal Diagn Therapy 15:174-176, 2000

Grebenc ML, de Christenson MLR, Burke AP et al. Primary cardiac and pericardial neoplasms: Radiologic-Pathologic correlation. Radiographics 20:1073-1103, 2000

Green KW, Bros-Koefoed R, Pollack P, et al: Antepartum diagnosis and management of multiple fetal cardiac tumors. J Ultrasound Med 10:697, 1991

Stanford W, Abu-Yousef M, Smith W: Intracardiac tumor (Rhabdomyoma) diagnosed by in utero iltrasound: A Case Report. J Clin Ultrasound 15:337, 1987

Dennis MA, Appareti K, Maco-Johnson ML, et al: The echocardiographic diagnosis of multiple fetal cardiac tumors. J Ultrasound Med 4:327, 1985

Gresser, C.D., Shime, J., Rakowski, H., et al: Fetal cardiac tumor: A prenatal echocardiographic marker for tuberous sclerosis. Am J Obstet Gynecol 156:689, 1986

Schaffer, R.M., Cabbad, M., Minkoff, H., et al: Sonographic diagnosis of fetal cardiac rhabdomyoma. J Ultrasound Med 5:531, 1986

Balain AA, Hogan TF: Cardiac Tumors. In Moller JH, Neal WA (Eds): Fetal, Neonatal, and Infant Cardiac Disease. Norwalk, Appleton and Lange, 1990, p 869

Ball Jr. WS, Prenger EC: Skull and Contents. In Kirks DR (Ed): Practical Pediatric Imaging, Diagnostic Radiology of Infants and Children, Second Edition. Boston, Little, Brown, and Company, 1991, p 113

Medley BE, McLeod RA, Houser OW: Tuberous Sclerosis. Seminars in Roentgenology 11:35, 1976  

 

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Peter W. Callen, M.D.
Professor of Radiology, Obstetrics, Gynecology and Reproductive Science
University of California Medical Center, San Francisco, California