Thoracic Pathology: A Volume in the High Yield Pathology Series 1st Edition

Cardiac Myxoma

Definition

• Most common primary neoplasm of the cardiac muscle in adults commonly arising from the endocardium, ranging in size from 1 cm to 10 cm

• Majority develop from the fossa ovalis in the left atrium, followed by the right atrium

• Rarely grows on both sides of fossa ovalis

• Ventricular or valvular sites are rare

• Tumor embolization is common and can be deadly

Clinical features

Epidemiology

• No known sex predilection

• Mean age at presentation is 50 years

• Unknown etiology; majority are sporadic; 10% associated with Carney syndrome

Presentation

• Presents with a clinical triad of valvular obstruction (tricuspid or bicuspid) with valvular damage, tumor emboli, and constitutional symptoms

• Arrhythmias leading to sudden death and abnormalities of atrioventricular conduction are seen because of disruption of the nodal or septal conduction system by the tumor

• If part of the Carney syndrome, it is more likely to be seen at a younger age, in atypical locations, and with increased risk of recurrence

Prognosis and treatment

• Complete surgical resection is curative, when possible

• Despite complete resection, risk of sudden death remains due to damage to the conduction system

• If the tumor is too large to resect, cardiac transplantation can be considered

Pathology

Gross

• Pale solitary, soft, gelatinous polypoid mass at fossa ovalis

• Can be sessile or pedunculated

• Cut surface may be variegated or diffusely calcified

• Some with surface thrombus

Histology

• Stellate or globular myxoma cells with abundant eosinophilic cytoplasm and indistinct cell borders arranged in cords, nests, rings, or poorly formed glands usually surrounding blood vessels

• Cells with oval nuclei, open chromatin, and indistinct nucleoli

• More cellular with mitotic activity near the surface; variable fibrosis and calcification

• Stroma consists of abundant myxoid substance containing chondroitin sulfate and hyaluronic acid

• Inflammation and hemorrhage are common

• Occasional Gamna-Gandy bodies (composed of fibrous tissue and elastic fibers with deposition of iron and calcium salts, completely disrupting the local architecture)

• Rarely, will have ossification, extramedullary hematopoiesis, mucin-forming glands, atypia, thymic rests

• May embolize to peripheral arteries

Immunopathology/special stains

• Positive for CD31, CD34, calretinin (cytoplasmic and nuclear staining), S100, vimentin

• Glandular components may be positive for keratin

• Negative for CD68, cytokeratin (except for glandular elements)

Main differential diagnoses

• Mural myxoid thrombi (no nests, cords, or rings; calretinin negative)

• Left atrial appendage thrombus

• Metastatic carcinoma

• Myxoid sarcoma

• Papillary fibroelastoma (on valve cusps, avascular papillary fronds)

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Fig 1 Cardiac myxoma. Stellate or globular cells with abundant eosinophilic cytoplasm and indistinct cell borders arranged in cords, nests, rings, or poorly formed glands usually surrounding blood vessels: low- (A) and high- (B)power images.

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Fig 2 Cardiac myxoma. Cardiac myxoma with mild chronic inflammation.

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Fig 3 Cardiac myxoma. Calretinin immunostain highlights the myxoma cells.



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