Case of primary malignant hemangiopericytoma of the heart expressing basement membrane-degradable enzymes.

Abstract

An echocardiogram demonstrated a large tumor in the left atrium of a 47-year-old woman with sudden heart failure. Emergent cardiotomy showed that the tumor arose from the left atrial wall, and almost entirely occupied the left atrium. Grossly, the tumor had partly undergone necrosis. Histologically, the tumor consisted predominantly of round to polygonal cells with ill-defined cell borders surrounding 'stag horn'-shaped blood vessels. Mitosis was frequently seen with abnormal mitotic figures. Immunohistochemically, the tumor cells diffusely expressed vimentin and focally expressed factor XIIIa and human leukocyte antigen-DR. A few tumor cells expressed S-100 protein or alpha-smooth muscle actin. Histopathological diagnosis was malignant hemangiopericytoma of the left atrium. Most tumor cells expressed matrix metalloproteinase (MMP)-2 and MMP-3, and several cells expressed MMP-9, all of which are capable of degrading a major component of basement membrane (i.e. type IV collagen). Furthermore, tumor cells expressed membrane type 1 MMP and tissue inhibitor of metalloproteinase-2, both of which are required for activation of proMMP-2. Fourteen months after the surgical removal, she died of systemic recurrent tumors.