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Mesothelial/Monocytic Incidental Cardiac Excrescences (Cardiac MICE)

Definition

Benign non-neoplastic proliferations of mesothelial cells admixed with histiocytes forming small excrescences attached to endocardium or free floating in pericardial cavity, incidentally detected.

Clinical Features

  • Benign
  • Non-neoplastic
  • No clinical significance

Pathogenesis

Histopathology

  • May be:
    • attached to the endocardium
    • free-floating in the pericardial cavity
    • inside an aortic dissecting aneurysm1,2,6
  • Admixture of mesothelial cells and histiocytes (Fig. 1
    So-called cardiac MICE. This process is composed of an admixture of plump histiocytes and ribbons of small cuboidal mesothelial cells.

    Fig. 1: So-called cardiac MICE. This process is composed of an admixture of plump histiocytes and ribbons of small cuboidal mesothelial cells.

    ):
    • mesothelial cells form:
      • strips
      • tubular and micropapillary formations
    • surrounded by smaller histiocytes
  • Often huge round vacuoles
  • Except for huge round vacuoles, appearance very similar to that of nodular mesothelial hyperplasia in hernia sacs7

Special Stains and Immunohistochemistry

  • Admixture of:
    • keratin-positive mesothelial cells
    • KP-1-positive histiocytes1 (Fig. 2
      So-called cardiac MICE. The immunostain for keratin highlights the mesothelial cell component, which is surrounded by the negative histiocytes and other mononuclear cells.

      Fig. 2: So-called cardiac MICE. The immunostain for keratin highlights the mesothelial cell component, which is surrounded by the negative histiocytes and other mononuclear cells.

      )

Diagnosis

  • Incidental microscopic findings:
    • at cardiac surgery (usually for valvular disease)
    • in endomyocardial biopsy

Differential Diagnosis

Select up to 2 differential diagnoses to compare with Mesothelial/Monocytic Incidental Cardiac Excrescences (Cardiac MICE)



  • Nodular mesothelial hyperplasia
  • Potential misdiagnosis as:
    • metastatic carcinoma
    • some other neoplasm

References

1 Luthringer DJ, Virmani R, Weiss SW, Rosai J. A distinctive cardiovascular lesion resembling histiocytoid (epithelioid) hemangioma. Evidence suggesting mesothelial participation. Am J Surg Pathol. 1990;14:993–1000.

2 Veinot JP, Tazelaar HD, Edwards WD, Colby TV. Mesothelial/ monocytic incidental cardiac excrescences. Cardiac MICE. Mod Pathol. 1994;7:9–16.

3 Courtice RW, Stinson WA, Walley VM. Tissue fragments recovered at cardiac surgery masquerading as tumoral proliferations. Evidence suggesting iatrogenic or artefactual origin and common occurrence. Am J Surg Pathol. 1994;18:167–174.

4 Walley VM, Peters HJ, Veinot JP, Courtice RW, Venance SL. The clinical and pathological manifestations of iatrogenically produced mesothelium-rich fragments of operative debris. Eur J Cardiothorac Surg. 1997;11:328–332.

5 Suarez-Vilela D, Izquierdo-Garcia FM. Nodular histiocytic/mesothelial hyperplasia: a process mediated by adhesion molecules?. Histopathology. 2002;40:299–300.

6 Bando Y, Kitagawa T, Uehara H, Sano N, Satake N, Onose Y, et al. So-called mesothelial/ monocytic incidental cardiac excrescences obtained during valve replacement surgery: report of three cases and literature review. Virchows Arch. 2000;437:331–335.

7 Rosai J, Dehner LP. Nodular mesothelial hyperplasia in hernia sacs. A benign reactive condition simulating a neoplastic process. Cancer. 1975;35:165–175.

Last updated: 3 Dec 2006

Mesothelial/Monocytic Incidental Cardiac Excrescences (Cardiac MICE)

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