2 CASES OF MESOTHELIAL MONOCYTIC INCIDENTAL CARDIAC EXCRESCENCES OF THE HEART/

Two cases of mesothelial/monocytic incidental cardiac excrescences in a 66-year-old female and an 80-year-old male are presented, Lesions ha d solid and tubular pattern formations which were composed of two pred ominant cell types of histiocytoid cells and cuboidal cells arranged i n strips, The histiocytoid cells were round and had well-defined nucle i with prominent nuclear grooves, They had a low nuclear to cytoplasmi c ratio, There were no atypical mitoses, Immunohistochemically, these cells were positive for leukocyte common antigen (LCA) and CD68 (KP-1) but negative for keratin, The cuboidal cells were present in strips, had haphazardly arranged surface microvilli and had small round non-cl eaved nuclei. These cells were positive for keratin but negative for L CA, CD68, p53, proliferative cell nuclear antigen, a-smooth muscle act in, Factor VIII, epithelial membranous antigen and vimentin. These les ions are probably reactive because of their heterogeneous components; an expected feature for an essentially artifactual lesion that is rela ted to cardiac surgery and invasive catheterization. Immunohistochemic al studies are useful for avoiding misdiagnosis of neoplasms.