Cardiac Tumors — Myxoma and Others

Myxoma-Specific Mechanisms

• Gelatinous matrix production: Myxomas are composed of embryonal connective tissue with abundant hyaluronic acid-rich mucopolysaccharide ground substance. This mucoid material lacks significant collagen or elastin, rendering the tumor soft and friable—characteristics that explain both its mobility within cardiac chambers and its propensity to embolize. The tumor cells produce this matrix through relatively low mitotic activity, resulting in slow growth but progressive expansion. The mucoid nature creates a characteristic appearance on cut section (gelatinous, translucent, glistening surface).

• Hemodynamic obstruction and ball-valve phenomena: Myxomas arising from the interatrial septum (75% of cases) can prolapse through the mitral valve during diastole, creating mechanical obstruction to left ventricular filling. This "ball-valve effect" produces intermittent or position-dependent hemodynamic compromise, accounting for syncope, dyspnea, and sudden positional symptoms. Right atrial myxomas similarly obstruct tricuspid inflow. The obstructive mechanism is purely mechanical rather than inflammatory or thrombotic, though secondary thrombus formation on the tumor surface frequently occurs due to blood stasis.

• Embolization and microinfarction: The friable nature of myxoma tissue, coupled with its endocardial location, predisposes to spontaneous embolization of tumor fragments or adherent thrombus. Emboli lodge in systemic or pulmonary vessels, causing infarction (brain, spleen, kidneys, limbs) or creating septic-like phenomena when sterile microemboli trigger inflammatory responses. This mechanism explains why myxoma patients present with stroke, peripheral arterial occlusion, or pulmonary infarction without other apparent embolic sources.

• Cytokine production and systemic inflammation: Myxoma cells produce IL-6, TNF-α, and other inflammatory cytokines, accounting for constitutional symptoms (fever, weight loss, malaise, arthralgia) that mimic infection or autoimmune disease. Serum levels of CRP, ESR, and IL-6 are frequently elevated. This paraneoplastic phenomenon can dominate the clinical picture, leading to diagnostic delay.

Other Cardiac Tumors: Rhabdomyosarcoma

• Embryonal sarcoma arising from myocardium: Rhabdomyosarcomas are skeletal muscle sarcomas (despite cardiac location) that arise from primitive mesenchymal tissue. They lack the mature differentiation seen in cardiac myocytes. Characterized by aggressive growth with early invasion into conduction tissue, wall perforation, and pericardial involvement. The embryonal variant (most common in heart) shows botryoid features with condensed cellularity at the periphery ("cambium layer" pattern).

Lipoma and Other Benign Tumors

• Mature adipose tissue hamartomas: Cardiac lipomas consist of normal, encapsulated fat cells without atypia or mitotic activity. They grow slowly and rarely cause hemodynamic compromise unless they involve the conduction system.

• Other benign tumors: Fibromas, hemangiomas, and teratomas arise from respective tissue elements and share low mitotic rates and non-invasive growth patterns.

Malignant Tumors: Angiosarcoma

• Endothelial malignancy with aggressive biology: Primary cardiac angiosarcomas arise from endothelial cells, typically in the right atrium or atrial wall. They show high mitotic activity, marked atypia, vascular proliferation with irregular slit-like lumina, and invasive growth. Necrosis and hemorrhage are common. Pericardial effusion and tamponade frequently develop due to wall perforation. Angiosarcoma carries the worst prognosis among primary cardiac tumors.

Myxoma

• Sporadic occurrence (~95% of cases): Most myxomas arise de novo without identifiable genetic predisposition or preceding conditions. No clear carcinogenic or mutagenic factors have been established.
• Familial myxoma syndrome (~5% of cases): Autosomal dominant inheritance linked to PRKAR1A gene mutations (protein kinase A regulatory subunit 1α) on chromosome 17q22-24. Part of Carney complex, a familial cancer syndrome characterized by myxomas (cardiac, skin, breast), pigmented skin lesions (lentigines, blue nevi), and endocrine tumors (pituitary adenomas, testicular tumors, adrenal adenomas). Familial cases present at younger age (mean 20-40 years vs. 55 years for sporadic) and are more often multiple or bilateral (10-25% of familial cases vs. <5% sporadic).

Rhabdomyosarcoma

• Young age and primitive mesenchymal differentiation: No clear environmental or genetic predisposition in sporadic cases. Occurs predominantly in children <5 years old.
• Genetic alterations: PAX-FKHR translocations (alveolar variant) or PAX-FOXO1 fusions can occur but are less common in embryonal forms.

Angiosarcoma and Other Malignancies

• No identifiable predisposing factors in most primary cardiac sarcomas.
• Secondary/metastatic tumors: Lung cancer, breast cancer, renal cell carcinoma, lymphoma, and melanoma most frequently metastasize to the heart (usually pericardium and right atrium). Metastases typically occur in advanced disease.

Cardinal Symptoms and Exam Findings

Constitutional symptoms (especially myxoma)

• Fever, weight loss, malaise, arthralgias, and myalgias due to IL-6/TNF-α production
• Mimics infection or rheumatologic disease, leading to diagnostic delay; misdiagnosis as endocarditis or lupus is common
• CRP and ESR markedly elevated out of proportion to clinical findings

Obstructive/hemodynamic symptoms (myxoma with ball-valve effect)

• Dyspnea and orthopnea from intermittent mitral obstruction
• Syncope or presyncope occurring with positional changes (especially lying flat); patients report relief when sitting upright
• Sudden cardiac death can occur when large myxoma completely occludes the mitral valve during diastole
• Physical exam: diastolic murmur (mimicking mitral stenosis) or tumor "plop"—a low-pitched diastolic sound from tumor prolapsing through valve

Embolic phenomena

• Acute stroke (most common embolic manifestation; occurs in ~25% of myxoma patients) from systemic embolization of tumor fragments or thrombus
• Peripheral arterial occlusion affecting limbs, spleen, kidneys
• Pulmonary infarction from right-sided tumors or paradoxical embolism
• Retinal artery occlusion or fundal hemorrhages

Arrhythmias and conduction abnormalities

• Atrial fibrillation from atrial irritation or wall invasion
• Atrioventricular block or ventricular arrhythmias when tumor involves conduction tissue (more common with angiosarcoma)

Presentation specific to tumor location

• Left atrial myxoma (most common, 75%): Mitral inflow obstruction, pulmonary congestion, dyspnea, orthopnea
• Right atrial myxoma (20%): Tricuspid inflow obstruction, hepatic congestion, ascites, peripheral edema
• Ventricular myxoma: Ventricular outflow obstruction; sudden death risk especially high with left ventricular involvement

Rhabdomyosarcoma presentation

• Usually diagnosed incidentally or at autopsy in young children
• Cardiac arrhythmias, heart failure, or pericardial effusion/tamponade as presenting feature
• Often advanced at presentation due to lack of symptoms in infants

Angiosarcoma presentation

• Pericardial effusion and tamponade (due to right atrial/wall origin and invasion)
• Syncope, dyspnea, shock from hemodynamic compromise
• Conduction disturbances and arrhythmias

Histological Findings (Myxoma)

Characteristic microscopic appearance

• Loose, myxoid stroma with abundant basophilic mucopolysaccharide ground substance (hyaluronic acid); stains with Alcian blue and colloidal iron
• Sparse cellularity with scattered spindle and stellate mesenchymal cells, often with cytoplasmic vacuoles
• Low mitotic rate (<1 per 10 HPF), minimal atypia, and no necrosis—features that distinguish myxoma from sarcomas
• Fibrovascular tissue at the periphery (peduncle or attachment site) contains larger blood vessels; thrombosis frequently present on the tumor surface
• Myxoid lipomas (variant) contain lipocytes intermixed with myxoid matrix
• Immunohistochemistry: Tumor cells express vimentin, smooth muscle actin (variable), and S100 (weak); do NOT express desmin or cardiac myocyte markers

Distinction from myxoid sarcomas

• Myxomas show far greater cellularity and atypia; marked mitotic activity argues against myxoma and suggests myxoid liposarcoma or leiomyosarcoma (which are extraordinarily rare in the heart)

Gross Pathology

Myxoma

• Gelatinous, glistening, translucent appearance with tan-white coloration
• Cut surface is soft and friable (not well-circumscribed but lacks true capsule)
• Size range: 1-10 cm (average 5-6 cm); rarely massive
• Sessile or pedunculated attachment; pedunculated tumors more likely to prolapse and embolize
• Frequently adherent thrombus on surface (gray-white, organized appearance)
• Location: 75% interatrial septum; 20% right atrium; 5% left atrium; rare in ventricles

Rhabdomyosarcoma

• Large, infiltrative, gray-tan mass with areas of necrosis and hemorrhage
• Poorly circumscribed with invasion into myocardium and frequently through epicardium
• Pericardial effusion commonly present

Angiosarcoma

• Tan-brown to purple infiltrative mass with extensive necrosis and hemorrhage
• Usually involves right atrium/wall with pericardial invasion
• Hemorrhagic pericardial effusion

Diagnostic Imaging

Echocardiography (TTE/TEE)

• First-line imaging; highly sensitive for detecting masses >1 cm
• Myxoma: Mobile, relatively homogeneous echo-dense mass arising from interatrial septum; prolapse through mitral valve during diastole visible
• Real-time imaging demonstrates position-dependent movement
• TEE provides superior anatomic detail and helps establish attachment site (critical for surgical planning)

Cardiac MRI

• Gold standard for characterizing tissue composition and assessing infiltration into myocardium or pericardium
• Myxoma: T1 isointense to myocardium, T2 hyperintense (reflects high water/mucopolysaccharide content); homogeneous enhancement
• Superior for detecting multiple tumors (Carney complex surveillance)
• Better assessment of pericardial involvement and extent of invasion

CT

• Useful for rapid assessment in acute presentations; less tissue characterization than MRI
• Detects calcification and hemorrhage

Cardiac catheterization

• Rarely performed for diagnosis; mainly historical significance
• Can precipitate acute hemodynamic compromise or embolization if catheter directly manipulates tumor—should be avoided

Laboratory Studies

Myxoma

• Elevated CRP and ESR (may be marked) in 50-60% of cases
• Elevated IL-6 levels (pathognomonic if present)
• Anemia (normocytic) in ~25% of cases, likely from chronic inflammatory state
• Elevated ferritin (nonspecific)
• ECG nonspecific; may show atrial fibrillation or nonspecific ST-T changes

Other tumors

• Laboratory findings nonspecific; mainly reflect hemodynamic compromise or systemic effects

Diagnostic Criteria

1. 1.Characteristic imaging findings (TTE/TEE/MRI) demonstrating mass attached to interatrial septum or atrial wall
2. 2.Tissue diagnosis (histopathology after surgical resection) confirming myxoid neoplasm with characteristic microscopic appearance
3. 3.Exclusion of mimics: thrombus (associated with AF or recent MI), vegetation (endocarditis), lipoma, or sarcoma

First-Line Treatment: Surgical Excision

Rationale and timing

• Complete surgical resection is curative for benign tumors (myxoma, lipoma, fibroma)
• Urgent/emergent surgery indicated for:
• Hemodynamically significant obstruction (dyspnea, syncope, severe hypotension)
• Large tumors with embolization risk
• Pericardial effusion with tamponade
• Intracardiac thrombus on tumor surface
• Elective surgery reasonable for smaller, asymptomatic myxomas discovered incidentally, though surveillance alone is rarely practiced due to unpredictable risk

Surgical technique

• Cardiopulmonary bypass with cardioplegic arrest essential to permit careful tumor removal and secure hemostasis
• Wide excision including tumor base and, when possible, a margin of normal tissue (especially important for avoiding recurrence with familial myxomas)
• Interatrial septum involvement may necessitate patch reconstruction (bovine pericardium or synthetic); careful dissection to preserve conduction tissue
• Biopsy during surgery confirms diagnosis (frozen section)
• Intraoperative TEE useful to assess complete removal and valvular competence

Results

• Complete symptom resolution in >90% of survivors
• In-hospital mortality <5% at experienced centers, higher (10-15%) with hemodynamic compromise or delayed presentation with thromboembolic complications

Second-Line Options

Malignant tumors (rhabdomyosarcoma, angiosarcoma)

• Neoadjuvant chemotherapy prior to attempted surgical resection (VAC regimen: vincristine, actinomycin-D, cyclophosphamide for rhabdomyosarcoma)
• Adjuvant chemotherapy and/or radiation post-resection
• Palliative intent in many cases given poor prognosis; overall 5-year survival <10% even with multimodal therapy

Heart transplantation

• Reserved for unresectable malignant tumors causing severe hemodynamic compromise when no other option exists (rare)
• Very poor outcomes given underlying tumor biology

Monitoring and Follow-Up (Myxoma)

Post-resection surveillance

• Clinical evaluation at 3-6 month intervals for first 2 years, then annually
• Echocardiography at 6-12 months post-op to assess for recurrence; then every 1-2 years
• Brain MRI rarely performed post-resection to detect silent emboli

Familial myxoma (Carney complex)

• Regular screening with echocardiography (every 1-2 years) given high recurrence/multiple tumor risk (10-25% recurrence in familial cases vs. 1-5% in sporadic)
• Skin, endocrine, and other surveillance per Carney complex guidelines

Embolization (Major Complication of

The classic stem

• Left atrial myxoma: middle-aged woman with fever, weight loss, elevated ESR/CRP, negative blood cultures, an embolic stroke, and a diastolic "tumor plop" with positional dyspnea. The IL-6–driven constitutional picture is the single most tested association — it makes the case look like culture-negative endocarditis or a vasculitis.
• Fossa ovalis of the interatrial septum is the classic stalk location, with the tumor body in the left atrium; pedunculated lesions prolapse into the mitral orifice in diastole (ball-valve), producing symptoms that change with body position — a finding true mitral stenosis does not show.

Best next step

• Transthoracic echocardiography is the initial test whenever a cardiac mass is suspected (consistent with ACC/AHA/ASE appropriate use criteria for echocardiography); TEE or cardiac MRI follows for attachment site and tissue characterization. Do not choose endomyocardial biopsy or catheterization — instrumenting a friable myxoma risks embolization.
• Surgical resection is the answer for management; myxoma is a surgically curable cause of stroke, so anticoagulation alone is a distractor.

Associations examiners repeat

• Carney complex: PRKAR1A mutation, autosomal dominant — myxomas (often multiple/recurrent, ventricular or biatrial), lentigines/blue nevi, and endocrine tumors including primary pigmented nodular adrenocortical disease. Young patient + multiple myxomas = look for skin pigmentation.
• Rhabdomyoma and tuberous sclerosis: TSC1/TSC2 (hamartin/tuberin) with loss of mTOR inhibition; the most common benign cardiac tumor of infancy/childhood, often multiple, and characteristically regresses spontaneously, so observation — not resection — is standard unless obstruction or arrhythmia occurs. mTOR inhibitors (e.g., everolimus) have been used for symptomatic lesions.
• Papillary fibroelastoma: most common valvular tumor; sea-anemone fronds on the aortic or mitral valve presenting with stroke or TIA.

Distractors to avoid

• Metastasis beats primary: metastatic disease (lung, breast, melanoma, lymphoma, renal cell) is far more common than any primary tumor; melanoma has the highest cardiac tropism.
• Myxoma is not a thrombus: an atrial thrombus sits in the appendage with atrial fibrillation or mitral stenosis, is immobile, and lacks a septal stalk.