Infected left atrial mass within anatomically normal heart.

A case is presented with some features of subacute bacterial endocarditis and of left atrial myxoma. Operative removal of a 5x3 cm tumour lying above and attached to an anatomically normal mitral valve reversed a rapidly deteriorating clinical situation. Histologically the entire tumour appeared to be old thrombus, and Gram-positive cocci in its superficial strata corresponded with Streptococcus viridans previously isolated from blood cultures. Many features, including an eight-year history of intermittent neurological disturbances and recent increasing hypergammaglobulinaemia, accord with the diagnosis of atrial myxoma. However, the valvular attachment site, absence of any cardiac structural abnormality, and tumour histopathology with bacterial colonization of the tumour present a unique situation which is explored in the discussion.