Myxoma

Myxoma is a benign tumor composed of myxoid connective tissue. It can arise in various tissues, but the term is most often applied to a tumor occurring in the heart, where it represents the most common type of primary cardiac neoplasm in adults.

Cardiac myxomas most commonly occur in the left atrium (about 75%), attached to the fossa ovalis by a stalk. They may cause obstructive symptoms resembling mitral valve disease, including dyspnea, orthopnea, and syncope, and can produce positional symptoms. Embolization from a friable surface can cause stroke or peripheral ischemia. Constitutional symptoms, such as fever and weight loss, may occur and can be due to interleukin-6 production.

Diagnosis relies primarily on imaging. Echocardiography is the standard initial test; transesophageal echocardiography provides detailed assessment. Cardiac CT or MRI can define anatomy and tissue characteristics. Definitive diagnosis is by surgical excision with histopathology, showing a myxoid stroma with scattered, spindle-shaped or stellate cells in a mucopolysaccharide-rich matrix.

Histology and immunohistochemistry: The lesion shows abundant extracellular ground substance with sparse cells; cells are typically positive for vimentin and may show other markers, but the profile is not specific.

Treatment is surgical resection with clearance of the stalk and surrounding tissue to reduce recurrence. Recurrence is uncommon in sporadic cases (approximately 2-5%), but is more frequent in familial settings, such as Carney complex. The prognosis after complete resection is generally favorable, though perioperative risk exists.

Carney complex is an autosomal dominant syndrome characterized by pigmented skin lesions, endocrine tumors, and recurrent cardiac myxomas. PRKAR1A mutations are commonly implicated. In addition to cardiac myxomas, myxomas may occur in other sites, but cardiac tumors carry the most clinical significance.