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Replacement of the background stain in the Taenzer-Unna acid Orcein method: contemporary perspective on research and histopathological diagnosis

The histochemistry is an important area of Histology whose purpose is to evidence, through dyes and reagents, the microscopic structures to make them more evident. For the performance of histochemical techniques in the laboratories of research and histopathological diagnosis, several substances are used, many of them are extremely toxic for the human being and the environment. In Brazil, the disposal of chemical residues is regulated by the National Environment Council (CONAMA) and the National Sanitary Surveillance Agency (ANVISA). The investment in reduction of residues is important, since the prevention is the safest way to mitigate the cost with residue management. In this sense, histological techniques must be reviewed and standardized in order to preserve the quality of analyzed material as well as the health of the worker and the environment, observing the principles of good laboratory practice. Although classical histochemical stains are still used in modern laboratories of research as well as pathology, there are no recent reports considering the revision and/or modification of these techniques during the last two centuries. The Orcein staining is used to demonstrate elastic fibers in paraffin embedded tissues, picric acid has been used as background staining. Considering that picric acid reveals high power of sublimation, that is, potentially explosive and with harmful effects to health, the objective of this study was to verify the possibility of replacement of the picric acid by another dye less toxic. For this, light green and orange G were tested. The results revealed the inefficiency of orange G in promoting greater contrast, while light green promoted to be an excellent background staining, highlighting the elastic fibers better when compared to orange G and picric acid. It is possible to conclude that histochemical techniques should be revised and/or adapted to preserve the health of the worker and the environment.

Keywords: histopathology, diagnosis, Orcein stain, environmental preservation

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