RESIDENT CASE STUDIES

Week 3 May 5 - May 9, 2003: Case 3   

Table of Contents | List of Diagnoses | Case 1 | Case 2 | Case 3 | Case 4

Discussion: Atrial Myxoma

Atrial myxoma is the most common benign endocardial neoplasm of the heart, and accounts for 75-80% of surgically resected cardiac tumors. Myxomas are more common in the left atrium (80%) than in the right atrium (20%). Patients with left atrial myxomas clinically present with mitral stenosis, ischemia of the extremities or brain  due to embolization (as in this case), arrhythmias, syncope, sudden death and constitutional symptoms. Right atrial myxomas usually present with recurrent pulmonary emboli, tricuspid valve obstruction, or endocarditis. Often patients present with manifestations of central nervous system. These lesions may be associated with myxoma syndrome, characterized by skin and mucous membrane lesions (blue nevi, myxoma  and ephelides -spotty pigmentation/lentiginosis), cardiac myxomas (often multiple and recurrent), mammary myxofibroadenoma and endocrine lesions (nodular adrenal cortical hyperplasia, pituitary adenomas), testicular sertoli cell tumors and psammomatous melanotic schwannoma. Some authors refer to the myxoma syndrome as Carney’s complex. 

Grossly, they can have a broad stalk or narrow pedicle with variegated, hemorrhagic, fibrotic and myxoid areas.. Microscopically, nests, cords or rings of stellate /ovoid cells (myxoma cells) with eosinophilic cytoplasm, and capillaries with indistinct cell borders in a myxoid background. Often, dense collections of histiocytes, lymphocytes, plasma cells, mast cells and hemosiderin laden macrophages are seen. Gamna bodies (degenerated calcified elastic fibers) are seen in a small percentage of the cases. Immunohistochemical stains are negative for cytokeratin (except intestine-like glands-positive for CK and CEA) and variably positive for S-100, smooth muscle and endothelial markers. Surgery is the treatment of choice with a 2% recurrence rate. 

Differential Diagnoses

Organizing thrombus: This can be confused especially with fibrotic myxoma. Lacks myxoma cells, extensive calcification and gamna bodies. Usually attached to the arterial wall. 

Hemangioma: Intracavitary hemangiomas can have myxoid background, but the capillary/ cavernous hemangioma background, lack of myxoid cells and abundant hemosiderin favor hemangioma. 

Sarcoma: Prominent myxoid background is seen in various types of sarcomas. But the large atypical cells arranged in different patterns, necrosis, and atypical mitoses favor sarcoma over myxoma. 

Metastatic carcinoma: Especially myxomas with glandular structures may be misdiagnosed as metastatic carcinomas. The important features to distinguish between these two lesions are presence of cellular atypia, mitoses and necrosis in carcinoma. The clinical history is always helpful and immunostains can be used sometimes to rule out carcinomas.

References:

Burke A, Virami R. (1996). AFIP Atlas of tumor pathology: Tumors of the heart and great vessels. AFIP, Washington DC. 

Virmani, R., Burke, A., Farb. Atlas of Cardiovascular Pathology.