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Tuesday, December 14, 2010

A Papillary Growth In The Left Ventricule

Autopsy of a 70-year-old woman reveals a papillary growth within the left ventricular chamber. The growth consists of a small mass of finger-like projections attached to the mitral valve, without associated valvular or other cardiac abnormalities. Histologically, each papillary structure is composed of a core of fibrous tissue lined by thickened endothelium. The patient did not have any history of cardiac disease or evidence of thromboembolism. Which of the following is the most likely diagnosis?

            A. Acute mural thrombus

            B. Cardiac myxoma

            C. Infective endocarditis

            D. Nonbacterial thrombotic endocarditis

            E. Papillary fibroelastoma


Explanation:

The correct answer is E. Gross and microscopic features of this small mass in the left ventricle are entirely consistent with papillary fibroelastoma. This lesion is not neoplastic, despite the sound of the name. It probably results from organized thrombi forming on the endocardial surfaces of the mitral valve or left ventricular cavity. Papillary fibroelastomas are usually clinically silent and are discovered at autopsy as an incidental finding.

An acute mural thrombus (choice A) would not have a core of fibrous tissue. Acute mural thrombosis usually develops as a result of stasis in the ventricular cavities, in association with ventricular enlargement, myocardial infarction, or ventricular aneurysm, for example. Thrombosis often develops in the atria when there is atrial fibrillation.

Cardiac myxoma (choice B) is the most frequent primary cardiac neoplasm. It is benign and consists of stellate mesenchymal cells within a myxoid background. Since the left atrium is the most frequent location, this tumor can produce mitral stenosis by a ball-valve effect.

Both forms of endocarditis are associated with formation of vegetations attached to the surface of the atrioventricular valves. Vegetations of infective endocarditis (choice C) are bulky and composed of fibrin, bacteria, and inflammatory cells.

Since nonbacterial thrombotic endocarditis (choice D) is caused by hypercoagulable states, the vegetations consist of aggregates of fibrin but few inflammatory cells and no bacteria.

Note that all of the above conditions may lead to systemic embolization. Fragments of vegetations, thrombi, myxoma, and papillary fibroelastoma may detach and be released into the bloodstream, causing infarcts.