So-called mesothelial/monocytic incidental cardiac excrescences obtained during valve replacement surgery: report of three cases and literature review

We present three cases of so-called mesothelial/monocytic incidental cardia c excrescences (MICE) of the heart and a brief review of related literature . Case 1 was a 51-year-old woman who underwent mitral- and aortic-valve rep lacement. A tissue sample was submitted as a thrombus attached to the left atrial endocardium. Case 2 was a 69-year-old woman who underwent mitral-val ve replacement. The sample was incidentally obtained as whitish clot-like f ragments, but its exact origin was not known. Case 3 was a 68-year-old woma n who underwent mitral-valve replacement for suspected infective endocardit is. The sample adherent to the pericardium was removed after valvular surge ry. Histologically, these lesions were composed of a mixture of plump histi ocytoid cells, a papillary arrangement of cuboidal cells, various sized vac uoles, and fibrin. The nests of cuboidal cells resembled cancer cells but s howed features of mesothelial cells and no proliferative activity, immunohi stochemically or ultrastructurally. In all cases, a suction tube placed in the left atrium was occasionally used to remove overflowing intrapericardia l fluid during the surgery. The tip of the suction tube was covered with sp iral wire, which is likely to transfer the stripped pericardial mesothelial cells to the left atrium. The significance of MICE is their possibility of being misdiagnosed as metastatic carcinoma by pathologists and a risk of a rterial embolization by mesothelial debris clinically.