A 57-year-old black female presented with a 1-month history of right-sided congestive heart failure clinical evidence of pulmonic tricuspid valvular stenosis insufficiency. The echocardiographic examination ventriculography demonstrated a large right atrial tumor interfering with the function of both right-sided valves. The patient underwent successful surgical resection of the tumor. Histologically, the tumor had cellular areas typical of myxoma, as well as glandular areas, a feature which has been described very rarely in this lesion. Electron microscopy of the glandular zones, which has never been reported previously, showed cells having essential homology with the usual myxoma elements. The atypical histopathology of this lesion supports the theory that atrial myxomas are true neoplasms, are not derived from unusually organized mural thrombi.