Mesothelial/monocytic incidental cardiac excrescence in a patient with antiphospholipid syndrome

Mesothelial/monocytic incidental cardiac excrescence (MICE) is a rare benign lesion composed of a mixture of histiocytes, mesothelial cells, fibrin, adipocytes and scattered inflammatory cells without a vascular network or supporting stroma. Its pathogenesis is controversial with some authors favoring an artifactual theory while others consider a reactive phenomenon. To date, only 41 cases of MICE have been reported in the literature. We describe an additional case of MICE in a 24-year-old female with antiphospholipid syndrome. A mobile hyperechogenic mass attached to the left ventricular surface of the aortic valve was documented by transthoracic echocardiography (TTE). The patient did have cardiac catheterization one month before the cardiac surgery. Histopathologic and immunohistochemical examination showed a lesion composed of histiocytes and mesothelial cells together with fibrin and scattered inflammatory cells. To our knowledge, this is the first case of MICE detected in a patient with antiphospholipid syndrome.