Application of scanning electron microscopy in the characterization of Aschoff nodules in rheumatic heart disease

Aschoff nodules (ANs) in excised atrial appendages from cases of rheumatic heart disease were examined with a scanning electron microscope (SEM). ANs could be identified with ease as nodular, fairly well defined cell aggregates lying in the subendocardium closely apposed to the myocardium. Cells comprising ANs were loosely packed in stacks. They were rectangular, oblong and angulated. The surface of some cells had fine ribbing while others were smooth having occasional blunt projections. SEM observations coupled with the findings of conventional and electron microscopy suggest that cells composing ANs are of mesenchymal origin having characters of epithelioid cells, reticular cells and/or fibroblasts.