The nature of the cardiac myxoma

Ten archive cases of cardiac myxoma were evaluated for proliferative activity, metastatic potential and expression of oncogene/tumour suppressor gene products by means of PCNA, MIB1, nm23, p53, Bcl-2 and Rb-1 immunohistochemistry. The myxomas showed variable proliferative activity (PCNA 0–41%, average 12.6%, MIB1 0–13%, average 3.2%) contrasting with the absence of mitotic activity histologically. All the myxomas showed nm23 staining. None showed p53 reactivity. Eight cases were negative for Bcl-2 expression, with two cases giving weak cytoplasmic staining. Rb-1 reactivity showed a variable pattern (staining indices 0–86%) paralleling the casesʹ proliferative activity. The cardiac myxoma is interpreted as a weakly proliferative lesion with little metastatic potential and no modulation of oncogene/oncogene suppressor products. Whilst not excluding a neoplastic aetiology, the results are considered more in keeping with a reactive/hamartomatous process.