Plastic-embedded endoscopic biopsies. Diagnostic advantages.

As the use of endoscopic biopsy has increased in recent years, the pathologists whose job it is to interpret these small specimens have been asked to give more specific diagnoses. Plastic embedding has proved to be a useful diagnostic tool because it provides better morphology than routine paraffin embedding and because enzyme histochemical and immunohistochemical markers can be used. We applied these techniques to endoscopic biopsies hoping to increase the diagnostic yield. Biopsies from 75 patients were fixed in paraformaldehyde, embedded in methacrylate, and sectioned at 2 mu. These sections were then compared with routine sections from the same patient. Additional special stains were used and enzyme histochemistry, or immunohistochemistry was performed on the plastic- or paraffin-embedded tissue as needed. We found that in 26.7% of the cases, plastic sections resulted in more specific diagnoses than was possible with paraffin sections. When distinguishing lymphomas from poorly differentiated carcinomas, this method provided much better morphologic differentiation and better demonstration of leukocyte common antigen than keratin staining. Identification of B- or T-cell antigens was possible on plastics but not on paraffin. Furthermore, lesions such as histiocytosis X and cryptosporidiosis were more accurately identified. Thus, we found that the plastic-embedded tissue provided all the information yielded by routine paraffin embedding and also improved the diagnostic yield on certain types of neoplastic or infectious processes.