Cardiac myxoma (sometimes called atrial myxoma) is the most common tumour of the heart. It can be sporadic (most of the cases) or associated with Carney complex.

The most common location is left atrium. Myxomas are usually solitary, may be quite large and have gelatinous ("myxoid") appearance. Due to the location in the area of constant turbulence, they often have surface ulceration, thrombi, and stromal hemorrhage, making it sometimes difficult to differentiate clinically from true mural thrombi. With chronic damage, other stromal changes, such as fibrosis, calcifications and even bone formation have been described.

Because the tumour is very friable, pieces may detach and embolize smaller vessels. Cells may also survive and grow in the vessel in the new location; however this is not considered a metastatic disease.

Patients present with symptoms associated with the tumour causing obstruction, such as chest pain, cardiac failure, syncope or sudden death. Other symptoms are related to the emobilization of other organs by tumour cells, for example with stroke if brain vasculature is affected.

Microscopically, the tumour consists of bland mesenchymal ("myxoma") cells, arranged in nests, cords or glandular structures in mucopolysaccharides-rich myxoid stroma. The cells are positive for CD34, CD31, calretinin and S100. Keratin may be positive. Factor VIII is usually negative.

Differential diagnoses include: non-neoplastic conditions, such as mural thrombi, valve vegetations (infectious, non-infectious), and tumours, primary to the heart or metastatic.

Treatment is surgical, recurrences are rare.