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Proliferating cell nuclear antigen expression grossly over-estimates cellular proliferation in cardiac myxomas
1University of Oxford Nuffield, Dept. of Pathology and Bacteriology, John Radcliffe Hospital, Oxford OX3 9DU, UK. derek.roskell@mailgate.JR2.ox.ac.uk.
Aims:
Myxomas are thought to be slowly growing benign neoplasms. Presentation is often due to embolic phenomena, though rapid increase in size is sometimes seen. Such an increase may be due to proliferation of cellular components, an increase in matrix due to synthesis or oedema, haemorrhage into the lesion, or the addition of surface thrombus. Routine microscopy suggests a low proliferation rate. The aim of this study was to investigate cellular proliferation, and to assess its contribution to tumour growth.
Methods:
The antibodies JC1, Ki67, PC10, and MIB1 were used to make an immunohistochemical assessment of proliferation in five cases of cardiac myxoma.
Results:
A significant difference was seen between number and type of cells stained with PC10 and the other markers. Whilst PC10 stained the nuclei of most (60 - 95%) endothelial and stromal cells in all cases, the other markers stained far fewer cells (up to 5%). All markers stained varying numbers of lymphoid cells.
Conclusions:
Proliferation in cardiac myxomas is unlikely to be rapid. The widespread positivity for PC10 suggests that PCNA is not a reliable marker in such tissues. Clinical cases in which myxomas have grown rapidly are probably due to changes in intercellular matrix rather than cellular proliferation.