Aetiology
The exact aetiology of atrial myxoma is unknown and most cases are sporadic. Familial atrial myxomas have an autosomal-dominant transmission, but these account for <10% of the total. Although familial myxomas may be transmitted without any associated disorders, they may present as a component of a Carney's complex, an autosomal-dominant condition comprising myxomas at various sites, endocrine tumours, and spotty pigmentation of the skin.[5][6][7]
Pathophysiology
The exact origin of myxoma cells remains uncertain, but they are thought to arise from remnants of subendocardial cells or multipotent mesenchymal cells in the region of the fossa ovalis, which can differentiate along a variety of cell lines. The hypothesis is that cardiac myxoma originates from a pluripotential stem cell, and myxoma cells express a variety of antigens and other endothelial markers.
Myxomas can be formed by pedunculation with a short broad base (85% of myxomas), but sessile forms can also occur.[4] Myxomas are yellowish, white, or brownish, and are frequently covered with thrombus.[3] The tumour size ranges from 1 cm to 15 cm and can weigh from 15 g to 180 g.[4] The surface of the myxoma is smooth in the majority of cases but it can also be friable or villous. The villous or papillary form of myxoma has a surface that consists of multiple fine or very fine villous, gelatinous, and fragile extensions that have a tendency to fragment spontaneously and are associated with embolic phenomena.[8] Histologically, myxomas are composed of myxoma (lepidic) cells, endothelial cells, smooth muscle cells, and an undifferentiated form embedded within an acid mucopolysaccharide ground substance and covered by endothelium.[9]
Classification
Benign primary cardiac tumours
Atrial myxoma is one of a number of benign primary cardiac tumours:
Myxoma
Papillary fibroelastoma
Fibroma
Fipoma
Rhabdomyoma.
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