Cardiac rhabdomyoma is the most common primary cardiac tumor of childhood, accounting for 60-80% of pediatric cardiac tumors. 50-90% of tumors are associated with tuberous sclerosis complex (TSC) — cardiac rhabdomyoma is found in 50-65% of TSC patients. Histopathologically, it is a hamartomatous tumor of myocyte origin containing characteristic 'spider cells.' Tumors are typically multiple (90%), well-circumscribed, solid, homogeneous intramural or intracavitary masses that can involve both ventricles. The most important clinical feature is that most undergo spontaneous regression within the first 4 years of life — therefore conservative follow-up is preferred in asymptomatic cases.
Age Range
0-5
Peak Age
1
Gender
Equal
Prevalence
Rare
Cardiac rhabdomyoma results from loss-of-function mutations in TSC1 (hamartin) or TSC2 (tuberin) genes. Normally, the hamartin-tuberin complex controls cell growth by inhibiting the mTOR (mechanistic target of rapamycin) pathway. Mutation-induced mTOR activation leads to abnormal proliferation of cardiac myocytes and increased glycogen accumulation. Rhabdomyoma cells ('spider cells') are large, vacuolated, glycogen-laden cells; the dense glycogen accumulation in the cytoplasm forms the basis of increased echogenicity on echocardiography and low density on CT. Spontaneous regression is attributed to physiological inactivation of the mTOR pathway in the postnatal period — therefore mTOR inhibitors (everolimus) are effective in accelerating regression. Multiple locations reflect the cardiac manifestation of TSC being a systemic genetic disorder affecting all body cells. Tumors typically locate intramurally in the ventricular septum, left ventricular free wall, and right ventricle, and when large can cause outflow tract obstruction or arrhythmias.
Detection of multiple, similarly sized and echogenic, well-circumscribed, homogeneous hyperechoic intramural masses in both ventricles and septum on fetal or neonatal echocardiography. This pattern is virtually pathognomonic for cardiac rhabdomyoma and is a strong indicator of tuberous sclerosis complex. This finding alone is sufficient indication to initiate TSC evaluation (cranial MRI, renal US, dermatological examination).
On fetal or neonatal echocardiography, hyperechoic (relative to myocardium), homogeneous, well-circumscribed, round or oval masses within ventricular myocardium (intramural) or protruding into the intracavitary space. Multiple lesions are present in over 90% of cases. Most commonly located in the left ventricle, ventricular septum, and right ventricle. Large lesions may narrow the ventricular outflow tract. Can be detected from 20-22 weeks on fetal echocardiography.
Report Sentence
Echocardiography demonstrates a total of _x_ hyperechoic (relative to myocardium), homogeneous, well-circumscribed intramural masses in both ventricles and interventricular septum, the largest measuring _x_ mm. Consistent with rhabdomyoma; tuberous sclerosis evaluation is recommended.
On color and spectral Doppler, large intramural or intracavitary rhabdomyomas may narrow the ventricular outflow tract causing increased gradient and turbulent flow. Left ventricular outflow tract obstruction (LVOTO) or right ventricular outflow tract obstruction can be clinically severe. Hemodynamically significant obstruction should be considered when pulsed-wave Doppler outflow velocity exceeds >2 m/s. Progressive gradient decrease is expected with tumor regression.
Report Sentence
Doppler demonstrates increased gradient (peak _x_ mmHg) and turbulent flow in the left ventricular outflow tract related to the intramural mass.
On non-contrast CT, iso-to-hypodense, homogeneous, well-circumscribed, round masses within ventricular myocardium. Shows slightly lower density than normal myocardium due to glycogen accumulation. Calcification is rare but may be seen during regression. CT is useful for evaluating total tumor count, sizes, and outflow tract relationship. In the pediatric population, CT is generally used as third-line imaging after echocardiography and MRI due to radiation dose concerns.
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CT demonstrates a total of _x_ homogeneous, well-circumscribed, mildly hypodense intramural masses in both ventricles and interventricular septum, the largest measuring _x_ mm.
On T1-weighted sequences, rhabdomyomas show isointense or mildly hyperintense signal relative to myocardium. Hyperintensity is related to intracellular glycogen accumulation shortening T1 relaxation time. Homogeneous signal pattern is characteristic — internal hemorrhage or necrosis is not expected. All multiple lesions show similar signal characteristics. Signal is preserved on fat-sat sequences (no fat content).
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On T1-weighted sequences, multiple intramural masses showing isointense-to-mildly hyperintense homogeneous signal relative to myocardium are seen within ventricular myocardium.
On T2-weighted sequences, rhabdomyomas show mildly hyperintense homogeneous signal relative to myocardium. T2 hyperintensity is less pronounced than the marked hyperintensity of myxoma. Tumor-myocardium contrast is more pronounced on T2, facilitating lesion detection. Hyperintensity may become more conspicuous on STIR sequences. All lesions show similar T2 signal intensity — this uniformity confirms that multiple lesions have the same histological structure.
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On T2-weighted sequences, intramural masses show mildly hyperintense homogeneous signal relative to myocardium. All lesions demonstrate similar signal characteristics.
On post-gadolinium sequences, rhabdomyomas show no enhancement or minimal enhancement. On LGE sequences, tumors demonstrate lower signal than surrounding myocardium (negative contrast). This finding reflects the homogeneous structure and low vascularity of the tumor. Absence of LGE in surrounding myocardium indicates no inflammation or fibrosis. Minimal heterogeneity may develop during regression.
Report Sentence
On LGE sequences, intramural masses show no enhancement; no pathological LGE is identified in surrounding myocardium.
On cine SSFP sequences, well-circumscribed, homogeneous masses within the ventricular wall (intramural) are seen. Unlike myxoma, intramural rhabdomyomas do not demonstrate independent mobility — they move with the myocardium. Lesions with intracavitary component may show partial cavitary protrusion. Cine sequences are critical for dynamically evaluating outflow tract relationship and effect on valve mechanism. In serial MRIs for regression monitoring, cine sequences provide reference for size comparison.
Report Sentence
On cine SSFP sequences, intramural masses move synchronously with myocardium without independent mobility. Outflow tract relationship has been evaluated.
Criteria
50-90% of all cardiac rhabdomyomas. TSC1 or TSC2 gene mutation. Multiple lesions typical. Association with cortical tubers, SEGA, renal AML, facial angiofibromas. Medical treatment option with mTOR inhibitor (everolimus) available.
Distinct Features
Multiple, bilateral ventricular, regression expected but everolimus if unsuccessful. Genetic testing and family screening mandatory. Cranial MRI for SEGA screening and renal US for AML screening required.
Criteria
Cases not meeting TSC criteria, genetic testing negative (10-50%). Usually single or few lesions. Other systemic findings of TSC absent. Spontaneous regression rate similar to TSC-associated cases.
Distinct Features
Single lesion, no TSC findings, genetic testing negative. Excellent prognosis, spontaneous regression expected.
Criteria
Intracardiac mass detected from 20-22 weeks on fetal echocardiography. May present with fetal arrhythmia or hydrops fetalis. Prenatal diagnosis is critical for postnatal TSC evaluation and delivery planning.
Distinct Features
Diagnosis in fetal period, hydrops fetalis risk in large lesions, pediatric cardiology coordination needed for delivery planning, postnatal TSC screening should be planned.
Distinguishing Feature
Fibroma is usually single, large, intramural in the LV wall, markedly T2 hypointense (fibrous content), and shows intense LGE. Rhabdomyoma is multiple, T2 mildly hyperintense, and shows no LGE. Calcification is common in fibroma, rare in rhabdomyoma.
Distinguishing Feature
Teratoma is usually single, pericardial or intracavitary, with heterogeneous internal structure (fat + calcification + cystic areas), mixed T1/T2 signal. Rhabdomyoma is intramural, homogeneous, multiple, and TSC-associated.
Distinguishing Feature
Myxoma is typically in adults, left atrial, single, pedunculated, markedly T2 hyperintense, with heterogeneous enhancement. Rhabdomyoma is pediatric, ventricular, multiple, intramural, homogeneous, and shows no enhancement.
Urgency
routineManagement
surveillanceBiopsy
Not NeededFollow-up
6-monthSince the vast majority of cardiac rhabdomyomas undergo spontaneous regression within the first 4 years, conservative follow-up (serial echocardiography every 6 months) is the standard approach in asymptomatic cases. In symptomatic cases (outflow tract obstruction, severe arrhythmia, heart failure), surgical resection or mTOR inhibitor (everolimus) therapy is applied — everolimus can reduce the need for surgery by providing rapid regression. TSC evaluation is mandatory in all cases: genetic testing (TSC1/TSC2), cranial MRI (cortical tubers, SEGA), renal US (AML), dermatological examination (hypomelanotic macules, angiofibromas). In fetal rhabdomyomas, if hydrops fetalis or arrhythmia develops due to large masses, delivery timing and location should be coordinated with pediatric cardiology.
Cardiac rhabdomyoma does not require surgery in most cases due to spontaneous regression — regular echocardiographic follow-up is sufficient. Surgery is indicated only for hemodynamic obstruction (outflow tract obstruction, valve dysfunction) or refractory arrhythmias. Genetic evaluation for tuberous sclerosis (TSC1/TSC2 mutation analysis) and brain MRI (cortical tuber, subependymal giant cell astrocytoma screening) should be performed in all cases. Everolimus (mTOR inhibitor) may accelerate regression.