DISCUSSION
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].
In conclusion, CMs are the most frequently diagnosed primary cardiac
tumor. They have characteristic imaging features that may frequently
suggest the diagnosis and aid in differentiating these lesions from
other intracardiac masses. This
study described clinical and echocardiographic characteristics of 5
patients with echocardiographic diagnosis of rare cardiac myxomas.
Cardiac tumors developed in unusual locations should be considered to
exclude the possibility of myxoma.
Disclosure
Yanhua Qi and Miaoyan Ma contributed equally to this work and should be
considered co-first authors.
Xiaopeng Li and Baomin Liu contributed equally to this work and should
be considered co- correspondence authors.