Mesothelial/Monocytic Incidental Cardiac Excrescences, So-called "Cardiac MICE": A case report

ABSTRACT

A rare case of mesothelial/monocytic incidental cardiac excrescences (cardiac MICE) is described in the aspect of pathological interest. This cardiac lesion is pathologically characterized by exuberant proliferation of mixed mesothelia and monocytes and might be misdiagnosed as metastatic carcinoma, rhabdomyosarcoma, and histiocytoid hemangioma, if the disease is not in the minds of pathologists. The reactive nodular hyperplasia due to irritation to mesothelia by various causes is a most prevailing pathogenetic mechanism. About 20 cases have been reported in the worldwide literature. A 67-year-old female patient presented with cough and dyspnea for 2 months, without any history of previous cardiac operation. 2D echocardiography of the heart revealed moderate amount of pericardial effusion with posterior wall thickening. Under the impression of metastatic malignancy, pericardiostomy was performed. Grossly, the tissue was dark hemorrhagic and friable and the histologic sections revealed the solid tumor-like proliferation of round to polygonal histiocytic cells admixed with small cuboidal mesothelial cells which formed strips and tubular arrays. They were found within the fibrinous network and there were scattered empty vacuolar spaces. Immunohistochemical staining confirmed their biphasic nature with the CD68 positivity of the histiocytes and the cytokeratin positivity of the cuboidal cells. Factor VIII positivity was not detected in any cell components. The lesion was considered the monocytic and mesothelial proliferation of reactive nature, so-called cardiac MICE in the pericardial cavity. We report a typical case of so-called MICE first in the Korean literature.