Mesothelial/monocytic incidental cardiac excrescences of the heart: case report and literature review.

Mesothelial/monocytic incidental cardiac excrescences (MICE) of the heart are rare benign entities that have only been diagnosed incidentally, following cardiac surgical procedure. To date, totally 35 cases have been reported in the English literature. We describe an additional case of cardiac MICE presenting with severe aortic regurgitation for aortic valve replacement in a 20-year-old Chinese male patient. On microscopic examination, the findings initially were confused with true neoplasm. However, the related gross appearance, clinical history and further immunohistochemical staining enabled an accurate diagnosis. We review the relevant literature and found that immunohistochemical staining, especially the anti-cytokeratin antibody (AE1/AE3) and KP1 (CD-68) that were used by most investigators previously, was significant while making the diagnosis, because the two components of the cells show a contrast immunoreactivity to these two makers. The pathologists should always be alert to this entity while diagnose a cardiac surgery specimen.