Discussion:
Degenerative mitral annulus calcification (MAC) is identified in 10.6%
of the population. Among them, only 0.6-0.7% present CMAC on
echocardiography. Their prevalence in autopsy series is higher (about
2.7% of MAC cases), suggesting underdiagnoses on imaging (1). It is
frequently observed in elderly women with hypertension and dyslipidemia
as well as in patients with kidney failure, in whom, it is linked to
calcium – phosphate metabolism deregulation (1, 2). However, caseous
necrosis of MAC is not clearly explained (3).The patient in our case is
young. We believe that the size of the calcification in her can be
explained by the radiotherapy she received that accelerated the process
of mitral valve degeneration. CMAC is often an asymptomatic condition
(as in the case we report) but patients can present with conduction
abnormalities or with embolization of caseous material (3). CMAC is a
dynamic process, can grow in size and infiltrate the adjacent myocardium
(4), as reported in our case. The center of CMAC contains liquefied
calcifications, cholesterol and fatty acids. Microscopic examination
shows a central amorphous acellular eosinophilic material with
macrophages and lymphocytes as well as peripheral fibrocalcic envelope
(1, 4, 5). These features explain the radiological findings. In fact, on
ultrasonography, CMAC has a central echolucency with a hyperechoïc rim,
a calcified envelop, no blood flow and no acoustic shadowing (3, 4). CT
confirms calcifications. The center is less hyperdense than the
periphery (4). CMR offers a better assessment of the mass that has a low
signal on T1W and T2W images. First pass perfusion shows no enhancement
whereas late gadolinium enhancement shows a peripheral enhancement (4).
Because of its scarcity, and variable appearance on ultrasound
examination, CMAC is frequently confused with infective myocarditis
vegetation, myocardial abscess, thrombus and cardiac tumor like in our
case (1, 3). Cardiac tumors include benign and malignant primitive
neoplasms as well as metastases. Primitive cardiac tumors are rare with
an incidence varying between 0.002 and 0.3% (2). Benign tumors include
myxomas, rhabdomyomas, papillary fibroelastoma, fibromas, hemangiomas,
lipomas, and leiomyomas (6). Myxoma is the most frequent benign type in
adults that often arises from the interatrial septum in the region of
the fossa ovalis and develops in the left atrium. It is generally a
mobile hypoechoic mass on ultrsonography, hypodense on CT.
Calcifications are observed in 14% of cases. It has a characteristic
signal on MRI. In fact, It is hypointense on T1W images, hyperintense on
T2W images, but may be heterogeneous, depending on its content.
Enhancement is generally patchy (1, 2, 6). Fibroelastoma is rare and is
located downstream the valve. It shows low signal on T2W images because
of its fibrous content and is isointense on T1W images (6). Hemangioma
is a vascular tumor that can be found in any chamber. It has typically a
heterogeneous high signal on T1W and T2 W images with intense
enhancement (5). Rhabdomyoma and fibroma are common in pediatric
population (6). Primitive malignant cardiac tumors are extremely rare
and are sarcomas in most cases. Malignancy is suggested by rapid growth,
invasion of adjacent structures, necrosis, hemorrhage, feeding vessels
and involvement of more than one chamber (6). Angiosarcoma is the most
frequent type in adults and typically arises in the right atrium. It has
a poor prognosis with a frequent metastatic spread (5, 6, 7). Metastases
are much more frequent and are found in 10-12% of patients with a
primitive cancer in post-mortem series (5). Primitive cancers spreading
to the heart include lung cancers, breast cancers, lymphomas and
melanomas (5). As the patient of the case we report had a history of a
treated breast cancer, metastasis was the first suggested diagnosis.
Metastases show low signal on T1W and high signal on T2W images with
heterogeneous enhancement (5).