CMs were the most frequent primary benign cardiac tumors in adults accounting for 50–85%. LA is the well-known, most prevalent site of myxomas with the incidence of 77–95% and 80% of which are attached to the interatrial septum. Tumors other than myxomas found in the LA cavity might be confused with myxomas and myxomas involving the sites other than the LA may be mistaken for other tumors. CMs are attached to the endocardium. There are two types of CMs: (1) round type, characterized by solid, round, regular shape and nonmobile surface; (2) polypoid type, characterized by soft, irregular shape and mobile surface. The polypoid type of tumor is associated with a higher occurrence of systemic embolism than the round type[9].
TTE is a widely available, noninvasive diagnostic method for initial evaluation of cardiac myxomas,with high sensitivity and specificity. Its accuracy can approach 95%[10]. It can usually provide adequate diagnostic information, such as location, attachment site, size, shape, mobility, morphology and hemodynamic consequences of the tumor.
Our study reported five rare sites of CMs diagnosed by TTE. The tumors at these sites should be distinguished from thrombi, papillary fibroelastoma(PFEs), leiomyoma, rhabdomyoma and lipoma. Some research reported that non-myxoma tumors were significantly smaller than myxomas[11]. Thrombi had comparable or larger size than myxomas. Importantly, in patients with AF or myocardial infarction, the diagnosis of thrombus should be considered primarily, even if it mimics myxoma. If a relatively small tumor is found outside the atrium, the possibility of myxoma should be considered after the exclusion of thrombus by history. However, it is very difficult to distinguish leiomyoma, lipoma, and myxoma by echocardiography, and in our case, one lipoma was misdiagnosed.
PFEs, which are mainly found in the valves, are rare benign tumors that can cause embolism. Cardiac valves were predominantly involved (76.5%); the most commonly valve affected was the aortic valve (29.4%), followed by the mitral valve (17.6%). Concurrent valvular disease was observed in 41.7% of patients. PFE is usually small, appears singly, and can cause potentially serious complications[12]. However, a tumor on the valve cannot be completely rule out as myxoma. Yuan S[13] reported a 47-year-old male with a cardiac mass arising from the tricuspid valve, which was misdiagnosed as a cystic myxoma. The mass turned out to be tricuspid cystic myxomatus degeneration with a primary cardiacleiomyoma finally. To our best of our knowledge, the pulmonary valve myxomas in our study have not been reported.
Giant stalkless myxomas had scarcely ever been reported in the literature[14]. Such myxomas are often immobile and require a more extensive surgical resection. Therefore, echocardiography and other multimodality imaging can be helpful in diagnosis and operation planning[15]. Case 5 in our study was a giant left atrial myxoma. Part of the left atrium was excised and repaired in operation. Nevertheless, a stalkless myxoma can result in low output state considering that it is a space-occupying lesion which is decreasing ventricular filling. In our case, decreasing ventricular filling can cause symptoms such as dizziness or syncope.
The clinical signs, manifestations, and symptoms produced are non-specific and determined by the location, size, and mobility of tumor[16]. There are 3 classic presentation for patients with CMs (“myxoma triad”): hemodynamic consequences, systemic embolism and constitutional or systemic manifestations. Smooth tumors are larger, occur with or without obstructive symptoms, whereas villous myxomas entailed a high embolic risk. This highlights the importance of the echocardiogram in describing the morphologic characteristics of these tumors, which predicts patients at higher risk of having an embolic complication and those who may require surgery as soon as possible after diagnosis. Even small and nonmobile cardiac myxomas with a round regular shape may cause recurrent cerebral infarction[17].