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).