Papillary Muscle Lipoma in a Teenage Patient With Review of the Literature

Graphical abstract


INTRODUCTION
Cardiac lipoma, which is exceedingly rare in both adult 1 and, particularly, pediatric 2 populations, has a broad spectrum of presentations. However, most are asymptomatic and detected in an investigation for other causes. 3 Due to the extremely low prevalence of cardiac lipomas arising from unusual papillary muscle sites, 4-7 the treatment is challenging, especially in the young.

CASE PRESENTATION
A 14-year-old boy with a chief complaint of atypical (chest wall) chest pain was referred to our department for transthoracic echocardiography (TTE) and further evaluation. The patient denied any cardiac problems in their personal or familial medical history. The patient's vital signs and physical examination were unremarkable. A TTE revealed a large homogeneously hyperechoic immobile mass without echolucency of the posteromedial papillary muscle and with normal appearance of the anterolateral papillary muscle (Figure 1, Videos 1 and 2). The left ventricle was normal in size and function, with mild eccentric to lateral wall mitral regurgitation ( Figure 2, Video 3). Color flow Doppler imaging showed no flow within the mass ( Figure 3). In the cardiovascular magnetic resonance imaging (CMR) study ( Figure 4, Videos 4 and 5), the posteromedial papillary muscle showed India ink artifact (type 2 chemical shift artifact) in balanced steady-state free precession (bSSFP) sequences, high signal intensity in T2-based sequences, and isointense signal intensity in short tau inversion recovery sequence as a T2 fat suppression sequence, all of which indicate fat-containing tissue. In the gadolinium study, no early gadolinium enhancement in the first pass perfusion (Video 6) or late gadolinium enhancement was detected, which also favors lipoma in the posteromedial papillary muscle.

DISCUSSION
Primary cardiac tumors are rare benign tumors. In adults, the incidence is between 0.2% and 0.4%, among which lipoma is an extremely rare benign tumor that accounts for 8% in autopsy series. 1 In patients younger than 18, rhabdomyoma is the most common car-diac tumor, followed by fibroma. The primary malignant tumors include rhabdomyosarcoma and fibrosarcoma. 2 Lipoma may occur in individuals of different ages and gender; however, it is more common among elderly patients. 1,8 Moreover, lipoma constitutes a minority of primary cardiac tumors in children, and only a few pediatric cases diagnosed with cardiac lipoma have been reported. 2 Lipomas are often intracardiac sessile masses originating primarily from the subendocardium (50%), followed by an equal distribution of the subepicardium and myocardium (25%). 9 In a systematic review in 2021, lipomas were mostly found to be located in the right atrium (42.4%) and left ventricle (33.3%) in different sizes. 10 We found only 3 cases of cardiac lipoma arising from papillary muscle through a PubMed search reviewed in Table 1.
In the review of these 3 cases, 2 had lipoma in the anterolateral papillary muscle and 1 in the posteromedial papillary muscle, as in the mentioned case. Koshy et al. 5 reported the first case in 2010, a middle-aged woman with a history of melanoma who underwent anterolateral papillary muscle lipoma resection due to an ischemic VIDEO HIGHLIGHTS Video 1: Two-dimensional TTE, rotated parasternal long-axis view, demonstrates a large homogeneously hyperechoic immobile mass of the posteromedial papillary muscle. Normal left ventricle systolic function is also noted. Video 2: Two-dimensional TTE, parasternal short-axis at the level of papillary muscle view, demonstrates an echo-dense mass-like lesion arising from posteromedial papillary muscle with normal appearance of the anterolateral papillary muscle. Video 3: Two-dimensional TTE, parasternal long-axis view with color flow Doppler, demonstrates mild eccentric, posteriorly directed mitral regurgitation (MR). Video 4: Two-chamber cine bSSFP CMR sequence demonstrates normal left ventricle size and function with a focally prominent posteromedial papillary muscle including the lipoma; an India ink (type 2 chemical shift) artifact is seen at the border of this mass indicating fat-containing tissue. Video 5: A stack of 3-chamber cines, bSSFP CMR sequences demonstrates the focally prominent posteromedial papillary muscle lipoma with the India ink (type 2 chemical shift) border artifact indicating fat-containing tissue. Video 6: Mid left ventricular, CMR first-pass perfusion sequence demonstrates normal myocardial perfusion and a focally dark mass that represents nonperfusion of the posteromedial papillary muscle with the lipoma. event. In 2016, Prestipino et al. 6 reported a middle-aged woman who was incidentally diagnosed with anterolateral papillary muscle lipoma during a checkup assessment. The patient was closely monitored due to the absence of symptoms. Kim et al. 7 published the latest case of cardiac lipoma in 2018 and reported a middleaged man with posteromedial papillary muscle lipoma who underwent surgery for a cardiac lipoma tumor as well as mitral valve replacement. Although a cardiac lipoma is usually asymptomatic, it may be incidentally detected while investigating other disorders. 4 However, depending on its location and size, it can cause symptoms such as chest pain, palpitations, arrhythmia, or even sudden cardiac death due to coronary artery or valve obstruction. 11 Transthoracic echocardiography is the first step in detecting a cardiac mass. If a cardiac mass cannot be defined or have a clear characterization through TTE, it is recommended that other imaging methods be utilized. Cardiac computed tomography and CMR have complementary values for evaluating cardiac masses. On cardiac computed tomography with and without contrast, a Hounsfield unit of less than -50 and enhancement after contrast administration suggest benign lipoma. Positron emission tomography can provide precise diagnostic information in determining cardiac tumors. 3,10 The echocardiographic findings of different cardiac masses are summarized in Table 2. [10][11][12][13][14][15] Acoustic characteristics alone cannot routinely differentiate benign lipomas from other malignant tumors, and CMR is the preferred complementary noninvasive imaging technique to assist in diagnosing cardiac masses since it offers improved tissue differentiation. Due to the very low prevalence of cardiac lipoma, there is no specific guideline for the treatment of such tumors. However, in symptomatic patients, surgery will be indicated. 4 Close follow-up by imaging modalities can detect any recurrence or changes in tumor size. 10 This case study presents a young patient with an unusual location of a cardiac lipoma in the posteromedial papillary muscle. After extensive consultation with the heart team, considering the mass size and the absence of clinical or hemodynamic symptoms, it was concluded that we should proceed with conservative management consisting of serial clinic visits, physical examinations, and TTE. Should there be any    changes in the TTE findings, a CMR should be performed to help guide treatment decisions.

CONCLUSION
Transthoracic echocardiography can primarily detect papillary muscle lipoma, and CMR can provide more details as a complementary mo-dality. Careful considerations are required according to mass location, size, and clinical symptoms to select an appropriate treatment method.

CONSENT STATEMENT
Complete written informed consent was obtained from the patient (or appropriate parent, guardian, or power of attorney) for the publication of this study and accompanying images.

ETHICS STATEMENT
The authors declare that the work described has been carried out in accordance with The Code of Ethics of the World Medical Association (Declaration of Helsinki) for experiments involving humans.

FUNDING STATEMENT
The authors declare that this report did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.