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Mesothelial/monocytic incidental cardiac excrescences: cardiac MICE
J P Veinot1, H D Tazelaar, W D Edwards
1Division of Anatomical Pathology, Mayo Clinic, Rochester, Minnesota.
Insights
Four new cardiac lesions, termed cardiac MICE, were identified. These mesothelial/monocytic growths may arise after cardiac catheterization and can be mistaken for cancer.
Area of Science:
- Cardiovascular Pathology
- Surgical Pathology
- Oncologic Pathology
Background:
- Cardiac lesions resembling histiocytoid hemangioma are rare.
- Understanding their origin and nature is crucial for accurate diagnosis.
Observation:
- Four incidental cardiac lesions were identified in patients aged 55-63.
- Three patients had a history of cardiac catheterization.
- Lesions were found during endomyocardial biopsy or mitral valve replacement.
Findings:
- The lesions were composed of histiocytes (macrophages) and cuboidal cells.
- Immunohistochemistry revealed biphasic nature: cytokeratin+ cuboidal cells and CD68+ histiocytes.
- Electron microscopy suggested mesothelial and monocytic origins.
Implications:
- These reactive lesions, named cardiac MICE (mesothelial/monocytic incidental cardiac excrescences), can be misdiagnosed as metastatic adenocarcinoma.
- A potential link to prior cardiac catheterization is suggested.
- Recognition of cardiac MICE is important to avoid misdiagnosis and unnecessary treatment.
Abstract:
We have identified four new cases of the cardiac lesion resembling a histiocytoid (epithelioid) hemangioma from the consultation and surgical pathology files of the Mayo Clinic from 1979 to 1992. The lesions occurred in two men and two women, mean age 60 yr (range, 55 to 63), three of whom had undergone previous cardiac catheterization. All were found incidentally, two as separate tissue fragments obtained by right ventricular endomyocardial biopsy during investigations for dilated cardiomyopathy, and two during mitral valve replacement (one free floating in the left atrium and the other attached to the mitral valve). The latter two lesions measured 1.0 and 0.8 cm. All were composed of histiocytes (macrophages) focally admixed with cuboidal cells which formed strips and tubular arrays in three cases. Immunohistochemistry (two cases) confirmed their biphasic nature with cytokeratin positivity of the cuboidal cells and CD68 (KP-1) positivity (macrophage-myeloid lineage) of the histiocytes. Carcinoembryonic antigen and Leu-M1 were negative for both cell types. Transmission electron microscopy (two cases) showed macrophage-like cells and cuboidal cells with intracytoplasmic intermediate filaments, desmosome-like cellular junctions, and rough endoplasmic reticulum consistent with mesothelial cells. All four patients had a benign clinical course (range, 2 mo to 13 yr). This mesothelial and monocytic (histiocytic) process is postulated to relate to previous cardiac catheterization (applicable in three of our patients). The importance of these nodules, which are likely reactive, is their potential confusion with metastatic adenocarcinoma. We propose the name mesothelial/monocytic incidental cardiac excresences (cardiac MICE) for these lesions.