17.2 Cardiac Masses, Thrombus, Tumor, Vegetation, and Mimics

Prove that a structure is real before naming it

A cardiac mass is first a descriptive imaging finding, not a pathologic diagnosis. Review cancer, infection, embolic event, AF, valve or device history, anticoagulation, indwelling catheter, recent infarction, surgery, and prior imaging. Acquire the suspected structure in orthogonal TTE planes and through the cardiac cycle. Change transducer position, frequency, depth, gain, focus, and insonation angle. A real structure remains anatomically coherent; reverberation, side-lobe, near-field clutter, and mirror artifact often move or disappear with the beam.

Describe chamber or valve, exact attachment, maximal dimensions, shape, border, echogenicity, homogeneity, mobility, stalk or broad base, independent motion, obstruction, valve dysfunction, and associated effusion. Record whether it is new or changed. Color assesses flow around or through a lesion but color mosaic is not tissue vascularity. Three-dimensional imaging may clarify attachment and spatial relation, while TEE improves evaluation of the LAA, atrial septum, valves, prostheses, and posterior structures. CT and CMR add tissue and extracardiac characterization. No modality feature alone makes a final histologic diagnosis.

Recognize common thrombus settings

Thrombus probability rises when location matches stasis or injured endocardium and prior imaging shows new development. Mobility and protrusion may increase embolic concern, but echogenicity does not reliably age a thrombus. Ultrasound-enhancing agents improve LV cavity definition and distinguish a filling defect from poorly opacified myocardium. An avascular mass usually does not enhance, yet absence of enhancement is not specific for thrombus; vegetation and some tumors can also be poorly vascularized. Do not start, stop, or recommend anticoagulation from the scanning room.

Distinguish tumor patterns without overcalling

A myxoma most often arises in the LA from a stalk near the fossa ovalis and may prolapse through the mitral valve, causing positional obstruction. It can be heterogeneous, mobile, or friable. Not every LA mass is a myxoma: thrombus, lipomatous septum, metastatic extension, and artifact remain alternatives. Papillary fibroelastoma is commonly a small mobile frondlike valvular mass; Lambl excrescences, vegetation, degenerative tissue, and thrombus overlap. Lipomatous hypertrophy thickens the interatrial septum while typically sparing the fossa ovalis, creating a dumbbell contour rather than an intracavitary tumor.

Metastatic involvement is more common than a primary malignant cardiac tumor. Look for pericardial effusion or thickening, myocardial infiltration, multiple lesions, and extension through the IVC, SVC, pulmonary veins, or great vessels. A broad-based irregular RA free-wall mass can suggest angiosarcoma, but CT, CMR, pathology, and clinical staging determine diagnosis. Tumor perfusion with an enhancing agent can support vascularity, and CMR can characterize tissue, yet overlap remains. The sonographer should report anatomy and hemodynamic effect, not announce benignity or malignancy.

Separate vegetation from sterile or normal tissue

Vegetation is typically an irregular independently mobile mass on the upstream side of a valve or infected material, accompanied at times by tissue destruction, new regurgitation, abscess, or prosthetic dehiscence. Echo cannot establish infection without clinical and microbiologic integration. Lambl excrescences, fibroelastoma, redundant chordae, calcific nodules, sutures, and nonbacterial thrombotic endocarditis can appear valvular. A negative TTE does not exclude endocarditis when suspicion is high, particularly with prosthetic valves or devices; TEE and repeat imaging may be required.

Normal structures are frequent traps. In the RA, recognize crista terminalis, Eustachian valve, and Chiari network; in the RV, moderator band and coarse trabeculation; in the LA, coumadin ridge and pectinate tissue near the appendage; in the LV, papillary muscles, false tendons, and trabeculations. Epicardial fat, caseous mitral annular calcification, prosthetic sutures, and catheter-related artifacts can also mimic masses. Confirm attachments in more than one plane and compare with expected anatomic location.

Escalate and communicate by risk

Use UEA, 3-D, TEE, CT, or CMR when the result will clarify a poorly seen border, attachment, vascularity, tissue, or extracardiac extension. State which chambers or appendages were inadequately visualized; “no mass seen” is not equivalent to exclusion in a limited study. A thrombus in transit, a mass intermittently obstructing an inflow or outflow valve, a highly mobile lesion with imminent hemodynamic risk, or destructive endocarditis complication requires immediate communication through laboratory policy. Final interpretation integrates clinical history, cultures, multimodality imaging, treatment response, surgery, or pathology.

Preserve uncertainty during follow-up

Serial behavior can refine probability without supplying pathology. Resolution during clinician-directed anticoagulation supports thrombus; growth, invasion, vascularity, or extracardiac extension raises tumor concern; new valve destruction with bacteremia raises infection concern. Confirm that plane, enhancement, and loading are comparable before calling change. Record the observation and relevant treatment interval, while leaving medication, biopsy, surgery, and final diagnostic decisions to the clinical team.

Location is evidence, not a diagnosis

A left-atrial mass near the fossa ovalis may suggest myxoma, while an apical mass in an akinetic LV may suggest thrombus. Neither pattern is definitive until mimics, other planes, clinical context, and appropriate advanced imaging are reconciled.