Cardiac Myxoma

Cardiac myxoma is the most common of the primary tumors of the adult heart, all of which are very rare. Cardiac myxoma is a benign neoplasm that arises from primitive multipotent mesenchymal cells. Most occur sporadically, but some are a part of some familial syndromes. All 4 chambers may give rise to myxoma, but 90% originate and grow in the atria, with a left-to-right ratio of approximately 4:1. Diagnosis is made by echocardiography, cardiac magnetic resonance imaging (MRI), or cardiac computed tomography (CT). Complete surgical excision is required because of the substantial risk of embolization and cardiovascular complications, including sudden death.

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Overview

Definition

Cardiac myxoma is a benign primary tumor of the heart.

Epidemiology

  • Primary cardiac tumors are very rare: incidence < 0.1%
  • Myxoma is the most common primary cardiac tumor.
  • Most common in adults, but can happen in all age groups
  • 90% of cardiac myxomas arise in the atria, with left-to-right ratio of 4:1.
  • Women > men
  • Most are sporadic.
  • Most common inherited form is a part of Carney complex:
    • Autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance disorder:
      • Atrial and extracardiac myxomas
      • Schwannomas
      • Pigmentation abnormalities
      • Endocrine and other tumors 
    • Not the same as Carney triad or Carney-Stratakis syndrome

Etiology

  • Arises from primitive multipotent mesenchymal cells 
  • No consistent genetic alterations in sporadic myxomas
  • Growth factors may contribute to tumor formation, e.g., vascular endothelial growth factor (VEGF), an angiogenic factor.
  • Familial syndromes with myxomas are associated with specific genetic defects:
    • Carney complex: null mutations in PRKAR1A, encoding a regulatory subunit of a cyclic-AMP–dependent protein kinase
    • Mazabraud’s syndrome: single or multiple intramuscular myxomas with fibrous dysplasia; activate mutations in the GNAS1 gene

Pathophysiology

Anatomy and histology

  • 80% originate in the left atrium (most commonly, fossa ovalis).
  • Most others are in the right atrium.
  • Range from 1–15 cm in diameter
  • Typically pedunculated tumors with gelationous consistency
  • Microscopic features:
    • Scattered stellate or globular cells in the mucopolysaccharide stroma
    • Can be accompanied by hemorrhage and chronic inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation
    • Small tumors tend to be villous and friable.
    • Larger tumors usually have a smooth surface.
Myxoma

Surgical gross pathology specimens (A, B, C, D, E) and histologic (F) findings of bilateral atrial myxomas
A: myxoma from left atrium
B: myxoma from right atrium
C: embolic myxoma from aortic bifurcation
D: embolic myxoma from left popliteal artery
E: embolic myxoma from right popliteal artery
F: histologic findings of myxoma (H&E (hematoxylin and eosin) x400): characteristic stellate tumor cells within an abundant myxoid stroma

Image: “Myxoma” by Division of Cardiology, Department of Internal Medicine, College of Medicine, Hanyang University, Seungdong-Gu, Heangdang-Dong 17, 133-070 Seoul, South Korea. License: CC BY 4.0

Pathophysiologic mechanisms

  • Obstruction of blood flow: causes heart failure
  • Interference with cardiac valves: 
    • More common with pedunculated myxomas
    • Regurgitation
  • Embolization:
    • More common with small tumors (from fragments or surface thrombi)
    • More commonly systemic than pulmonic
  • Direct invasion of the myocardium:
    • Left ventricular dysfunction
    • Arrhythmias/heart block
    • Pericardial effusion Pericardial effusion Pericardial effusion is the accumulation of excess fluid in the pericardial space around the heart. The pericardium does not easily expand; thus, rapid fluid accumulation leads to increased pressure around the heart. The increase in pressure restricts cardiac filling, resulting in decreased cardiac output and cardiac tamponade. Pericardial Effusion and Cardiac Tamponade
  • Invasion of the adjacent lung (can mimic lung cancer Lung cancer Lung cancer is the malignant transformation of lung tissue and the leading cause of cancer-related deaths. The majority of cases are associated with long-term smoking. The disease is generally classified histologically as either small cell lung cancer or non-small cell lung cancer. Symptoms include cough, dyspnea, weight loss, and chest discomfort. Lung Cancer)
  • Cytokine production (e.g., interleukin-6)

Clinical Presentation

Left-side myxomas (approximately 85%)

  • Symptoms similar to mitral valve stenosis or regurgitation (left heart failure):
    • Dyspnea
    • Orthopnea
    • Paroxysmal nocturnal dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea
    • Cough/ hemoptysis Hemoptysis Hemoptysis is defined as the expectoration of blood originating in the lower respiratory tract. Hemoptysis is a consequence of another disease process and can be classified as either life threatening or non-life threatening. Hemoptysis can result in significant morbidity and mortality due to both drowning (reduced gas exchange as the lungs fill with blood) and hemorrhagic shock. Hemoptysis
    • Edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema
    • Fatigue
  • Neurologic symptoms: secondary to systemic emboli
  • Arrhythmias

Right-side myxomas (approximately 15%)

  • Symptoms of tricuspid disease (right heart failure):
    • Fatigue
    • Peripheral edema
    • Hepatomegaly
    • Ascites Ascites Ascites is the pathologic accumulation of fluid within the peritoneal cavity that occurs due to an osmotic and/or hydrostatic pressure imbalance secondary to portal hypertension (cirrhosis, heart failure) or non-portal hypertension (hypoalbuminemia, malignancy, infection). Ascites
    • Syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope
    • Sudden death
  • Pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism
  • If patent foramen ovale Patent Foramen Ovale A patent foramen ovale (PFO) is an abnormal communication between the atria that persists after birth. The condition results from incomplete closure of the foramen ovale. Small, isolated, and asymptomatic PFOs are a common incidental finding on echocardiography and require no treatment. Patent Foramen Ovale is present:
    • Systemic emboli
    • Hypoxemia (from shunting of venous blood from the right side)

Constitutional symptoms

  • May be seen in 30% of patients 
  • Cytokine release:
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
    • Weight loss
    • Fatigue

Diagnosis and Management

Physical examination

  • Left atrial tumors:
    • Diastolic “tumor plop” on auscultation
    • Pulmonary edema Pulmonary edema Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary Edema: rales or crackles on auscultation
  • Right atrial tumors:
    • Diastolic murmur
    • Jugular venous distention
    • Generalized edema
    • Hepatomegaly
    • Abdominal ascites

Imaging

  • Echocardiography (usually 1st imaging technique):
    • Transesophageal echocardiography (TEE) gives better resolution.
    • Can usually identify:
      • Mass
      • Mobility
      • Obstruction
      • Embolization 
  • Cardiac magnetic resonance imaging (CMR): detailed anatomic imaging
  • Cardiac computed tomography (CCT): if CMR not available
  • Positron emission tomography (PET) scan helps differentiate:
    • Metastatic tumors versus atrial myxoma 
    • Lipomatous septal hypertrophy versus atrial myxoma
  • Coronary angiography: 
    • “Sea anemone” appearance on angiography
    • Mapping of blood supply: may be needed for surgical planning

Transvenous biopsy

  • Risk of embolism
  • Should only be performed if diagnosis is uncertain and benefits outweigh the risks

Management

  • Surgical resection is required because of:
    • Risk of embolization
    • Cardiovascular complications
    • Risk of sudden death
  • Prognosis: 
    • Operative mortality rate < 5%
    • Recurrence: 2%–5% of cases, more common if familial or multiple
    • Cardiac autotransplantation (with atrial reconstruction) or transplantation may be necessary for recurrent atrial myxoma.
    • Atrial arrhythmias or atrioventricular conduction abnormalities in 26%
Gross pathology of excised left atrial myxoma

Gross pathology of excised left atrial myxoma, measuring 7 × 6 × 4 cm: Note the translucency of the tumor, due to its abundant content of acid mucopolysaccharide ground substance.

Image: “Gross pathology” by Department of Neurology, Hospital of International University of Health and Welfare, 537-3 Iguchi, Nasushiobara, Tochigi 329-2763, Japan. License: CC BY 3.0

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Differential Diagnosis

Benign primary cardiac tumors or tumor-like masses

  • Intracardiac thrombus: the most common type of intracardiac mass in adults. May occur following myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction with ventricular thrombus formation, or with atrial fibrillation Atrial fibrillation Atrial fibrillation (AF or Afib) is a supraventricular tachyarrhythmia and the most common kind of arrhythmia. It is caused by rapid, uncontrolled atrial contractions and uncoordinated ventricular responses. Atrial Fibrillation and mitral stenosis Mitral stenosis Mitral stenosis (MS) is the narrowing of the mitral valve (MV) orifice, leading to obstructed blood flow from the left atrium (LA) to the left ventricle (LV). Mitral stenosis is most commonly due to rheumatic heart disease. Mitral stenosis leads to impaired LV diastolic filling, increased LA pressure, and LA dilation. Mitral Stenosis where atrial thrombi predominate. Left-sided thrombi are a common source of stroke and other arterial embolic syndromes. Ultrasound and CMR aid in the diagnosis. Treatment is usually with anticoagulation.
  • Rhabdomyoma: the most common pediatric cardiac tumor; a benign neoplasm of muscle cells, often multiple, associated with tuberous sclerosis Tuberous sclerosis Tuberous sclerosis or tuberous sclerosis complex (TSC) is an autosomal dominant disorder with mainly neurocutaneous symptoms. Mutation in the TSC genes causes excessive tumor-like growths in the brain, eyes, heart, kidney, and lungs. Cutaneous manifestations include hypopigmentation (i.e., ash leaf spots, confetti lesions) or excessive growth (i.e., angiofibroma, shagreen patch). Tuberous Sclerosis. Frequently undergoes spontaneous regression; diagnosis is made by clinical impression and imaging.
  • Fibromas: 2nd most common primary pediatric cardiac tumor. Composed of fibroblasts, which usually arise in ventricular septum. Fibromas may be part of Gorlin syndrome (nevoid basal cell carcinoma Basal cell carcinoma Basal cell carcinoma is the most common skin malignancy. This cancer arises from the basal layer of the epidermis. The lesions most commonly appear on the face as pearly nodules, often with telangiectatic blood vessels and ulceration in elderly individuals. Basal Cell Carcinoma syndrome); does not regress, but may not need treatment if small.
  • Lipomas: rare encapsulated neoplasm of mature fat cells. May originate from subendocardium, subpericardium, or from the myocardium. Lipomas are more frequent in the left ventricle or right atrium.
  • Papillary fibroelastoma: the 2nd most common primary cardiac tumor in adults. Papillary fibroelastoma are small sea anemone–shaped endocardial tumors with frond-like structures, usually on mitral or aortic valves, where they can cause symptoms due to embolization, either of the tumor itself or thrombus. Imaging is diagnostic, and surgery is recommended.

Malignant tumors of the heart

  • Sarcoma: malignant tumor originating from the connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue cells. Exceedingly rare in the heart. Angiosarcoma is the most common type. Prognosis is poor, as these tumors tend to grow rapidly and recur even when completely resected.
  • Metastatic tumors: 20 times more common than primary tumors. May be present in 20% of patients dying of cancer. Symptoms depend on the site of cardiac involvement. Diagnosis is made with echocardiography, CMR, or CCT.

References

  1. Valvular Heart Disease. (2020). In Kumar, V., Abbas, A. K., Aster, J.C., (Eds.). Robbins & Cotran Pathologic Basis of Disease. (10th ed., p. 579).
  2. Gaasch, W.H., Salm, T.J.V. (2020). Cardiac tumors. UpToDate. Retrieved December 17, 2020, from https://www.uptodate.com/contents/cardiac-tumors?search=Atrial%20myxoma&source=search_result&selectedTitle=1~46&usage_type=default&display_rank=1#H12461347
  3. Kuon, E., Kreplin, M., Weiss, W., Dahm, J.B. (2004). The challenge presented by right atrial myxoma. Herz. 2004 Nov;29(7):702-9. doi: 10.1007/s00059-004-2571-7. PMID: 15580325.

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