Primary cardiac tumors (PCTs) are rare, with a prevalence of 0.002%–0.3% in autopsy studies and 0.15% in echocardiographic series. Despite their rarity, they are clinically significant, as even benign tumors can cause hemodynamic complications, thromboembolic events, and arrhythmias.

Cardiac lesions can be subdivided into pseudomasses and true masses. The latter can be divided into non-neoplastic and neoplastic, which can be classified into benign and malignant (Table 1).

Table 1: Classification of cardiac masses. Abbreviations: LA - left atrium; RA - right atrium; RAA - right atrium appendage; RV – right ventricle; IAS - interatrial septum; LHIS - lipomatous hypertrophy of the interatrial septum.

Benign tumors account for 70%–75% of PCTs, with myxomas (30%–50%), papillary fibroelastomas (15%–20%), and lipomas (10%–15%) being the most common in adults. In children, rhabdomyomas predominate. Malignant tumors account for 25%–30%, with angiosarcomas most common in adults (10%) and rhabdomyosarcomas (5%–6%) in children. Metastatic cardiac tumors are 20–40 times more common than primary ones, often affecting the pericardium.

Non-neoplastic cardiac masses are the most frequent and include intracardiac thrombi, pericardial cysts, aneurysms, hematomas and others (Fig. 1, Fig. 2, Fig. 3, Fig. 4).

Fig 1: Round, well-defined mass in the right cardiophrenic angle (blue arrow) is seen on SSFP images (a). It has fluid signal characteristics, appears isointense on T1 (b), hyperintense on T2FS sequence (c), and shows no contrast uptake (d), consistent with a pericardial cyst. SSPF = Steady-state free precession sequence. LGE = late gadolinium enhancement.

Fig 2: Patient with dilated cardiomyopathy. The initial CT pulmonary angiography scan (a-c) shows filling defects in the right atrium, indicated by the orange and blue arrows (a, b), and in the left ventricle, marked by the green arrow (c). The MRI phase of early gadolinium enhancement (d-h) confirmed multiple thrombi in the cardiac chambers: at the coronary sinus ostium (blue arrow, d), the right atrial appendage (orange arrow, h), the apex of the right ventricle (yellow arrow, f), and multiple thrombi in the left ventricle (green arrows, e-h).

Fig 3: Patient with a history of trauma. A fluid collection in the pericardial cavity, marked with blue arrows, compressing the right ventricle, is seen on CTA (a) and MRI (b-g) images. The collection has high attenuation (54 HU) on CTA and a heterogeneous, hyperintense signal on T1FS and T2FS sequences, consistent with a hematoma. On MRI contrast sequences, pericardial thickening and enhancement of inflammatory origin are observed. SSPF = Steady-state free precession sequence, LGE=late gadolinium enhancement, SSPF = Steady-state free precession sequence.

Fig 4: Several cases of aneurysms and pseudoaneurysm in the heart, marked with blue arrows.

Pseudomasses are anatomical cardiac structures or embryologic reminants and if prominent can raise suspicion of true mass with echocardiography, but are easily characterized with MRI or CT (Table 2).

Table 2: Pseudomasses of the heart and their key multimodality imaging findings. Abbreviations: LA - left atrium; RA - right atrium; RAA - right atrium appendage; RV – right ventricle; IAS - interatrial septum; IVC - inferior vena cava; LHIS - lipomatous hypertrophy of the interatrial septum.

Clinical presentation is usually related to its location, although some may produce systemic symptoms (Fig. 5,  Table 3, Table 4). The clinical context is crucial for diagnosis. For example, cardiac thrombi are often linked to atrial fibrillation or ventricular dysfunction, while vegetations are associated with valve disease, fever, and bacteremia. In contrast, pseudomasses are usually asymptomatic.

Fig 5: Most common locations of cardiac masses.

Table 3: Clinical manifestations of cardiac tumors.

Table 4: Factors determining tumor etiology.

Multimodality imaging using echocardiography, MRI, CT, and PET-CT is key to differentiating between these masses (Table 5, Table 6). While biopsy remains the gold standard, multimodality imaging often identifies the tumor's nature, and signs of malignancy noninvasively (Table 7). Furthermore, histologically confirmed real-life examples provide valuable insight into the pathological and imaging correlation of these masses, facilitating more accurate diagnoses in clinical practice.

Table 5: Imaging modalities for cardiac tumor evaluation.

Table 6: T1, T2, T2* relaxation times of cardiac masses in comparison to normal myocardium: ⬆️ - higher , ⬇️ - lower, = equal.

Table 7: Key differential aspects of malignant and benign cardiac masses.