Histologic detection of fat emboli

We describe a procedure for detection of fat emboli in formalin fixed tissue using osmium tetroxide postfixation. Intravascular fat in tissue postfixed in osmium tetroxide, embedded in epoxy or paraffin, and stained with toluidine blue, hematoxylin, or Oil Red O is more easily visualized than in frozen tissue that is stained with Oil Red O. With these methods, fat emboli may be detected years after the initial autopsy.