9.5 Cardiac Tumors & Intracardiac Masses in Children
Key Takeaways
- Rhabdomyoma is the most common primary cardiac tumor of childhood, accounting for roughly 60% of pediatric cardiac tumors; it appears as multiple well-circumscribed hyperechoic intramural masses in the ventricular myocardium and septum, and 50% to 80% of affected children have tuberous sclerosis complex.
- Rhabdomyomas characteristically regress spontaneously during infancy and early childhood, so asymptomatic lesions are observed rather than resected; mTOR inhibitors such as everolimus and sirolimus can accelerate regression when obstruction or arrhythmia demands it.
- Fibroma is the second most common pediatric primary cardiac tumor and behaves oppositely: it is solitary, large, homogeneous, often centrally calcified, situated in the left ventricular free wall or interventricular septum, and it does not regress, carrying a real risk of ventricular arrhythmia and sudden death.
- Intrapericardial teratoma arises at the base of the heart attached to the great vessels, appears as a heterogeneous multicystic mass, and typically presents in the fetus or neonate with a massive pericardial effusion and tamponade physiology.
- Myxoma is the most common primary cardiac tumor across all ages but is uncommon in young children; it is a mobile, lobulated left atrial mass attached by a narrow stalk to the fossa ovalis that prolapses through the mitral orifice, and in a child it should prompt evaluation for Carney complex.
9.5 Cardiac Tumors & Intracardiac Masses in Children
Clinical Core: Content outline task 3.A.18 asks the candidate to identify the characteristics of cardiac tumors. Pediatric cardiac oncology is dominated by benign lesions: more than 90% of primary cardiac tumors in children are benign, and the single most common one, rhabdomyoma, usually disappears on its own. The exam-relevant skill is not making a tissue diagnosis but describing a mass precisely enough that the differential collapses: where it sits, how many there are, how echogenic it is, how it attaches, how it moves, and what it obstructs.
Rhabdomyoma: The Pediatric Default
Rhabdomyoma accounts for roughly 60% of primary cardiac tumors in children and is the lesion most often found on fetal echocardiography.
| Feature | Characteristic |
|---|---|
| Number | Multiple in the great majority of cases |
| Location | Intramural within the ventricular myocardium, interventricular septum, and, less often, the atrial walls |
| Echogenicity | Homogeneously hyperechoic (brighter than surrounding myocardium), well circumscribed, non-calcified |
| Mobility | Fixed and intramural; may bulge into the cavity but is not pedunculated |
| Natural history | Spontaneous regression during infancy and early childhood in most cases |
| Syndromic association | Tuberous sclerosis complex (TSC1 hamartin, TSC2 tuberin) in 50% to 80% |
Because the association runs so strongly the other way as well, the discovery of multiple cardiac rhabdomyomas in a fetus or neonate mandates evaluation for tuberous sclerosis: cerebral cortical tubers and subependymal nodules on brain imaging, hypopigmented ash-leaf macules on Wood lamp examination, renal angiomyolipomas, and retinal hamartomas.
When Rhabdomyomas Matter Hemodynamically
Most are incidental. The three ways they cause trouble are:
- Outflow tract obstruction — a septal or subvalvar mass producing a late-peaking, dagger-shaped continuous-wave Doppler signal in the left or right ventricular outflow tract.
- Inflow obstruction — an atrioventricular valve-level mass producing an elevated mean diastolic inflow gradient.
- Arrhythmia — rhabdomyomas are a well-recognized substrate for ventricular tachycardia and for Wolff-Parkinson-White accessory pathways, because tumor tissue can bridge the annular fibrous insulation.
When obstruction or arrhythmia is life-threatening in a neonate, mTOR inhibitors (everolimus, sirolimus) are used to shrink the tumor and frequently avoid surgery.
Fibroma: The Solitary Non-Regressing Mass
Cardiac fibroma is the second most common pediatric primary cardiac tumor and is the clinical mirror image of rhabdomyoma.
- Solitary and often very large relative to the heart.
- Left ventricular free wall or interventricular septum, intramural.
- Homogeneous with a characteristic tendency to central calcification, producing a bright focus with acoustic shadowing that rhabdomyomas do not show.
- Does not regress.
- High rate of ventricular arrhythmia and sudden cardiac death, which drives surgical resection even in asymptomatic children.
- Associated with Gorlin syndrome (nevoid basal cell carcinoma syndrome, PTCH1).
Intrapericardial Teratoma
- Arises from the base of the heart, attached to the aorta or main pulmonary artery within the pericardial sac.
- Heterogeneous and multicystic on two-dimensional imaging, often with calcification.
- Presents in fetal life or the neonatal period with a massive pericardial effusion and tamponade, hydrops, or respiratory distress rather than with an intracardiac mass effect.
- Pericardiocentesis stabilizes; resection is curative.
The Remaining Pediatric Differential
| Tumor | Location and appearance | Key clinical point |
|---|---|---|
| Hemangioma | Any chamber or the pericardium; heterogeneous, sometimes with visible vascular channels on color Doppler | May cause pericardial effusion; can regress |
| Papillary fibroelastoma | Small (usually < 1.5 cm), highly mobile, frond-like, attached to a valve surface by a short stalk; shimmering speckled edge | Rare in children; embolic rather than obstructive risk |
| Myxoma | Left atrium, attached by a narrow stalk to the fossa ovalis; lobulated, heterogeneous, prolapses through the mitral orifice in diastole | Most common primary cardiac tumor overall but uncommon in young children; in a child, evaluate for Carney complex |
| Malignant primary tumors | Rhabdomyosarcoma, angiosarcoma, undifferentiated sarcoma; infiltrative, ill-defined margins, pericardial invasion, hemorrhagic effusion | Rare; broad-based infiltration rather than a discrete stalk |
| Metastatic and contiguous tumors | Lymphoma, leukemic infiltration, Wilms tumor and hepatoblastoma extending up the inferior vena cava into the right atrium, neuroblastoma | Far more common than primary malignancy; always interrogate the IVC from the subcostal window in a child with an abdominal tumor |
Masses That Are Not Tumors
Roughly half of pediatric "cardiac mass" consultations turn out to be a non-neoplastic finding. The sonographer's job is to recognize the mimics on sight:
| Mimic | Where it lives | Distinguishing feature |
|---|---|---|
| Thrombus | LV apex (low ejection fraction), right atrium at a catheter tip, Fontan pathway, prosthetic valve | Broad-based, laminated, non-mobile or sluggish; associated stasis or foreign body |
| Vegetation | Low-pressure side of a valve, along a regurgitant jet, on a device | Shaggy, chaotically oscillating, with fever and positive cultures |
| Chiari network | Right atrium, from the IVC orifice to the crista terminalis | Thin, fenestrated, whip-like, extremely mobile; benign embryonic remnant |
| Eustachian valve | Posteroinferior right atrium at the IVC junction | Crescentic membranous flap directed toward the fossa ovalis; benign |
| Prominent moderator band / crista terminalis | RV apical third / posterolateral right atrium | Muscular, continuous with the wall, moves with the myocardium |
| Lipomatous hypertrophy of the atrial septum | Interatrial septum, sparing the fossa ovalis | Classic dumbbell shape; echobright and fatty |
The Systematic Scanning Approach
A mass report that answers these six questions is almost always sufficient for the clinical team:
- Compartment: intramural (within myocardium), intracavitary, valvular, or pericardial. This one distinction eliminates most of the differential immediately.
- Number: multiple intramural ventricular masses in an infant is rhabdomyoma until proven otherwise; a solitary large ventricular mass is fibroma.
- Echotexture: homogeneous and hyperechoic (rhabdomyoma), homogeneous with central calcification (fibroma), heterogeneous and cystic (teratoma), infiltrative and ill-defined (malignancy).
- Attachment: narrow stalk (myxoma, papillary fibroelastoma) versus broad-based or intramural (rhabdomyoma, fibroma, sarcoma).
- Hemodynamic effect: interrogate the inflow and outflow tracts with color and spectral Doppler for obstruction; measure gradients; assess atrioventricular and semilunar valve competence; quantify any pericardial effusion and look for tamponade physiology (right atrial systolic collapse, right ventricular diastolic collapse, exaggerated respiratory inflow variation, plethoric IVC).
- Ventricular function and rhythm context: document baseline systolic function, and flag the tumor types that carry arrhythmic risk.
Cardiac magnetic resonance imaging is the complementary study for tissue characterization when echocardiography cannot resolve the differential, particularly for distinguishing fibroma from rhabdomyoma and for defining the resection plane of an infiltrating lesion.
Exam-Day Traps
- Importing adult epidemiology. Myxoma is the correct answer for an adult; in a neonate or infant with multiple bright intramural ventricular masses, the answer is rhabdomyoma.
- Calling a prominent Chiari network or eustachian valve a mass. Both are benign remnants and both live in the right atrium near the IVC; their thin, fenestrated, whip-like motion is diagnostic.
- Missing tumor extension from the abdomen. A child with a renal or hepatic mass needs a deliberate subcostal IVC-to-right-atrium sweep.
- Overlooking the pericardium. A neonate presenting with tamponade and no obvious intracardiac mass may have an intrapericardial teratoma at the base of the great arteries.
- Forgetting to look for obstruction. A tumor report without inflow and outflow Doppler interrogation is incomplete, because obstruction, not the mass itself, is what triggers intervention.
A term neonate has a fetal diagnosis of multiple cardiac masses. Postnatal echocardiography shows four well-circumscribed, homogeneously hyperechoic intramural masses in the interventricular septum and both ventricular free walls, without calcification. Ventricular function is normal and there is no outflow obstruction. What is the diagnosis and what extracardiac evaluation is mandatory?
A 4-year-old presents after an aborted sudden cardiac death event. Echocardiography demonstrates a single large homogeneous intramural mass in the left ventricular free wall with a bright central focus producing acoustic shadowing. The mass has been documented on imaging since infancy without any change in size. What is the most likely diagnosis and its expected natural history?
During a routine study on a 7-year-old, a thin, highly mobile, fenestrated filamentous structure is seen in the right atrium extending from the inferior vena cava orifice toward the region of the crista terminalis, whipping rapidly with each cardiac cycle. The child is afebrile with normal function. What is this structure?
A 3-year-old with a large abdominal mass undergoing staging is referred for echocardiography. Which specific imaging maneuver is most important in this clinical context?