Abstract
The fine structure of a case of differentiated rhabdomyosarcoma of the ear is described. Characteristic actomyosin filaments have been demonstrated in thin sections showing cross-striation (Z bands). There were large numbers of ribonucleoprotein particles but no virus-like particles present. It is hoped that, as in other difficult or rare tumours, electron microscopy may provide an additional clue of some assistance to the pathologist in determining diagnosis or aetiology.