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.