Tissues for light and electron microscopy are traditionally processed separately. Different fixatives and embedding media are usually employed. Paraffin is unsuitable for electron microscopy and the small amounts of tissue generally embedded in plastic makes sampling a significant problem for the light, as well as the electron microscopist. Techniques, however, have been described for plastic embedding of large samples of tissue which can be sectioned at 1 μm. The added resolution of these thinner sections potentially increases the diagnostic ability of the light microscopist. These techniques have not been fully utilized in pathology. If one fixative were utilized and the quantity embedded in plastic were comparable to that which is normally processed for paraffin, then the investigator could use plastic sections for better light microscopic evaluation with the option of subsequent examination of the same region in the same block at an ultrastructural level.
