From the archives of MD Anderson Cancer Center. Mesothelial/monocytic incidental cardiac excrescence with a review of the literature

Mesothelial/monocytic incidental cardiac excrescence (MICE) is a rare benign lesion composed of monocytes and mesothelial cells that is most often encountered during cardiothoracic surgery. We describe a case in a 71-year-old man with known aortic valve stenosis who presented with gradual onset dyspnea over a few weeks, made worse with minimal exertion. A transesophageal echocardiogram revealed severe aortic stenosis and mild pericardial effusion. The patient underwent aortic valve replacement, coronary artery bypass, and amputation of the left atrial appendage. Histological examination of a 0.8 cm blood clot received along with the atrial appendage showed an aggregation of bland cells with features of monocytes associated with small strands and nodules of mesothelial cells, fat cells, fibrin and a minute fragment of bone. Immunohistochemical analysis showed that the monocytic cells were positive for CD4 and CD68 (strong) and negative for calretinin and keratin. By contrast, the mesothelial cells were positive for calretinin and keratin and negative for all other markers. In sum, the morphologic and immunohistochemical findings support the diagnosis of MICE. Based on our review of the literature, about 60 cases of MICE have been reported previously which we have tabulated. We also discuss the differential diagnosis.

Primary and secondary cardiac tumors: clinical presentation, diagnosis, surgical treatment, and results

Cardiac tumours are some of the rarest primary tumours, while cardiac metastasis are more common yet still relatively rare. Seventy five percent of primary cardiac tumours are benign tumours. Cardiac tumours present with a range of obstructive, embolic, arrhythmic or systemic symptoms, and in many cases may present asymptomatically. The clinical presentation depends largely on the size and location of the mass. With advances in cardiac imagining and the introduction of cardiopulmonary bypass, the diagnosis and surgical treatment of these rare tumours has improved the prognosis and outlook for benign and malignant tumours. Management depends on tumour histology, size and location as well as the clinical presentation. Conservative management is reserved for small, benign tumours that can undergo regular echocardiographic follow-up. Symptomatic benign tumours are treated with surgical resection and the results are excellent. Malignant primary cardiac tumours have a poor prognosis with high rates of relapse and a median survival of 10-24 months.

Cardiac Excrescences of Unusual Origin

Mesothelial/monocytic incidental cardiac excrescences (cardiac MICE) are a rare finding that are most often discovered incidentally either upon echocardiography or invasive cardiovascular procedures. In total, less than 50 known cases have been reported since first being discovered over 30 years ago. They are typically benign lesions; however, there has been a reported case of cardiac MICE being responsible for severe cardiopulmonary compromise and another case of the lesion embolizing leading to cerebral infarctions and ultimately death. Cardiac papillary fibroelastomas are also uncommon lesions found in the heart though they are not as rare as cardiac MICE. They are also benign and are typically attached to valvular surfaces; however, they also can be found as mobile masses. Just as cardiac MICE, they are capable of causing turbulent flow and thrombus formation and have been reported as the cause of ischemic events due to their ability to embolize. We present a case of cardiac MICE and cardiac papillary fibroelastoma in an individual who initially presented with neurologic symptoms concerning for a cerebrovascular accident. The patient was found to have a left ventricular mass composed of both cardiac MICE and cardiac papillary fibroelastomas.

Occurrence of mesothelial/monocytic incidental cardiac excrescences in material from open-heart procedures: case reports and literature review

Mesothelial/monocytic incidental cardiac excrescences (MICE) are unusual findings during the histological analysis of material from the pericardium, mediastinum, or other tissues collected in open-heart surgery. Despite their somewhat worrisome histological appearance, they show a benign clinical course, and further treatment is virtually never necessary. Hence, the importance of recognizing the entity relays in its differential diagnosis, as an unaware medical pathologist may misinterpret it for a malignant neoplasm. Other mesothelial and histiocytic proliferative lesions, sharing very close histological morphology and immunohistochemistry features with MICE, have been described in sites other than the heart or the mediastinum. This similarity has led to the proposal of the common denomination "histiocytosis with raisinoid nuclei." We report three cases from the pathology archives of the Heart Institute of São Paulo University (Incor/HC-FMUSP), diagnosed as "mesothelial/monocytic incidental cardiac excrescence," with immunohistochemical documentation, and provide a literature review of this entity.

Fibromyxoid excrescence of the aortic valve that manifested after catheterisation and required resection

A 2-year-old boy developed fibromyxoid excrescence of the aortic valve 2 years after balloon dilatation for simple coarctation. Transthoracic echocardiography showed a mobile mass on the non-coronary cusp of the aortic valve. Definitive diagnosis was achieved after operative resection. This pathology was attributed to injury during catheter manipulation. Catheterised patients should be followed up carefully to avoid missing morphological changes.

Mesothelial/monocytic incidental cardiac excrescence mimicking cardiac tumor

Mesothelial incidental cardiac excrescence is a non-neoplastic tumor-like lesion commonly occurring in the intracardiac region. The exact etiology is unclear. A 32-year-old woman presented with respiratory distress on exertion. Echocardiography showed severe aortic, mitral, and tricuspid regurgitation, for which triple-valve replacement was performed. A small cardiac excrescence was found over the aortic valve, measuring 0.6 × 0.3 × 0.3-cm, which on microscopy showed features of mesothelial/monocytic incidental cardiac excrescence. This condition is very rare but it must be recognized because it mimics a metastatic malignancy.

Lesion of aggregated monocytes and mesothelial cells: mesothelial/monocytic incidental cardiac lesion

A 58-year-old woman with a history of childhood acute rheumatic fever and resultant mitral valve stenosis was admitted to our cardiovascular surgery clinic complaining of tachycardia, dyspnea, and chest pain. After clinical and radiological findings were evaluated, mitral valve replacement, tricuspid De Vega annuloplasty and plication, and resection of giant left atrium were performed. Atrial thrombus was removed from the top of the left atrial wall. Operation material considered as thrombus was sent to a pathology laboratory for histopathological examination. It was diagnosed with mesothelial/monocytic incidental cardiac lesion (cardiac MICE). Microscopic sections revealed that morphological features of the lesion were different from thrombus. The lesion was composed of a cluster of histiocytoid cells with abundant cytoplasm and oval shaped nuclei and epithelial-like cells resembling mesothelial cells within a fibrin network. Epithelial-like cells formed a papillary configuration in the focal areas. Mitotic figures were absent. Here we present a case which was incidentally found in a patient who underwent mitral valve replacement surgery, as a thrombotic lesion on the left atrium wall.

Nodular histiocytic aggregates in the greater omentum of patients with ovarian cancer

Nodular histiocytic aggregate (NHA) of the omentum is a rare benign proliferative process composed predominantly of histiocytes with scattered mesothelial cells. NHA is a differential diagnosis for neoplasms or metastatic tumors in cancer patients. To further clarify this clinical pitfall issue, the authors investigated surgical samples of the greater omentum from 96 patients with gastrointestinal malignancies and 53 patients with gynecologic neoplasms. Visible NHA of greater omentum was identified in 3 patients with ovarian neoplasms (borderline mucinous cystadenoma, low-grade papillary serous cystadenocarcinoma, and juvenile granulosa-cell tumor) but in none of the patients with gastrointestinal malignancies. Similar lesion was also identified on the cell blocks from peritoneal washings in 1 of the 3 patients. Grossly, the lesions formed small yellow-red nodules on the greater omentum, and the NHA lesion was also found diffusely on the surface of the appendix and fallopian tubes in 2 of the 3 patients. Histological study showed that typical NHA changes over an inflammatory background, which may indicate that NHA is a consequence of a chronic inflammatory process of omentum. The predominant infiltration of T lymphocytes in the NHA lesions indicates that the aggregation of histiocytes may be related to the activation of T-cell immunity. This report has first demonstrated visible NHA in the greater omentum of patients with ovarian malignancies, and awareness of this entity should be brought to clinicians to avoid misdiagnosis.

A case of mesothelial/monocytic incidental cardiac excrescence and literature review

Mesothelial/monocytic incidental cardiac excrescence (MICE) is a rare entity which is an amalgam of mesothelial cells, histiocytes, and fibrin, often found occasionally during cardiac valve replacement. We report a case in a 25-year-old Chinese female with serous mitral stenosis and patent foramen ovale. Routine and immunohistochemical stains and ultrastructure examination revealed the vegetation was predominantly composed of histocytes with scattered mesothelial cells. In fact nodular histiocytic/mesothelial hyperplasia (NHMH) is a similar lesion to MICE. MICE and NHMH could be unified, and NHMH may be a better choice.