Cardiac Masses, Tumors & Thrombi

Overview of Cardiac Masses

Most masses encountered on echocardiography are not true neoplasms. Thrombi, vegetations (covered with infective endocarditis in Chapter 8), and normal anatomic variants are all far more common than primary cardiac tumors. When a mass is identified, systematic characterization of location, attachment (broad-based versus stalk/pedunculated), mobility, echogenicity/texture, and border definition — supplemented by contrast enhancement, multiplane TEE, or cardiac MRI/CT when needed — guides the differential diagnosis and downstream management.

Primary Cardiac Tumors

Myxoma is the most common primary cardiac tumor in adults, accounting for roughly half of all primary cardiac tumors. Approximately 75-80% arise in the left atrium, classically attached by a stalk to the fossa ovalis on the interatrial septum. Myxomas are typically mobile, heterogeneous in echogenicity (may contain calcification or areas of hemorrhage), and can prolapse across the mitral valve in diastole, producing an obstructive, mitral-stenosis-like physiology or exertional syncope; they also carry a meaningful embolic risk because fragments can break off and travel systemically.

Papillary fibroelastoma is the most common tumor arising from a cardiac valve, as opposed to myxoma, which is the most common cardiac tumor overall. It typically presents as a small, mobile mass with a characteristic frond-like, "shimmering" appearance, attached by a short stalk to a valve surface — most often the aortic or mitral valve, usually on the downstream (low-pressure) side of the valve. Despite its small size, it carries significant embolic risk, including stroke or, if aortic-valve-based, coronary embolism.

Cardiac sarcoma, most commonly angiosarcoma, is the most common malignant primary cardiac tumor in adults. It frequently arises in the right atrium, grows rapidly with infiltrative extension into surrounding structures, and carries a poor prognosis. Rhabdomyoma and fibroma are the most common primary cardiac tumors in children but are not typical adult-exam content.

Risk Stratification and Multimodality Follow-Up

Embolic risk for both myxoma and papillary fibroelastoma correlates with mobility and size: highly mobile masses, or fibroelastomas exceeding roughly 1 cm, are more likely to embolize and more often prompt surgical excision even when the patient is asymptomatic. Most sporadic myxomas are solitary, but a minority are multiple, recurrent, or familial — seen in Carney complex, an autosomal dominant syndrome that also features skin pigmentation abnormalities and endocrine tumors — and these patients warrant closer surveillance and consideration of family screening.

Because 2D and Doppler findings alone cannot always distinguish tumor type or reliably exclude malignancy, cardiac MRI (tissue characterization, contrast enhancement pattern) and, when embolic or biopsy questions remain, cardiac CT or surgical pathology are frequently used to complete the work-up. TEE also outperforms TTE for detecting small, mobile masses on valve surfaces, given its higher spatial resolution and closer proximity to the heart.

Metastatic (Secondary) Tumors

Metastatic tumors are dramatically more common than primary cardiac tumors — by some estimates 20- to 40-fold more common — and most frequently involve the pericardium rather than the myocardium, often presenting first as a pericardial effusion. Common primaries include lung and breast carcinoma, melanoma, and lymphoma; renal cell carcinoma is notable for direct venous extension through the inferior vena cava into the right atrium, a pattern the sonographer should specifically look for when a renal mass history is present.

Cardiac Thrombi

Left atrial appendage (LAA) thrombus develops most often in the setting of atrial fibrillation or mitral stenosis, where left atrial enlargement and reduced appendage emptying velocities promote blood stasis. Because the trabeculated appendage is poorly visualized transthoracically, TEE is required for reliable exclusion, and thrombus must be carefully distinguished from the normal pectinate muscles that line the appendage wall.

LV apical thrombus forms over regions of apical akinesis or dyskinesis — classically after an anterior myocardial infarction with apical aneurysm formation, or in non-ischemic cardiomyopathy with severely reduced ejection fraction. It typically has a layered, laminated appearance. Because the apex is a common site of near-field echo dropout on transthoracic imaging, contrast (LV opacification) should be used whenever apical thrombus is suspected but not clearly seen on unenhanced images.

Normal Anatomic Variants (Mass Mimics)

Recognizing these variants prevents unnecessary work-up, anticoagulation, or biopsy referral for a structure that requires no intervention — an important distinction from a genuine mass with real embolic or obstructive potential.

A useful practical rule when a mass is first seen: correlate location and clinical context before reaching for an exotic diagnosis. A mobile RA structure near the IVC/eustachian valve in an otherwise asymptomatic patient is almost always a Chiari network; a septal structure that spares the fossa ovalis and has a soft, homogeneous fat-like texture is almost always lipomatous hypertrophy; and thin filiform strands along a valve closure line in an older adult are almost always Lambl's excrescences. Reserving concern for masses that are large, broad-based, invasive into adjacent structures, or associated with pericardial effusion and systemic symptoms keeps the differential appropriately weighted toward the common, benign explanations.