A high-performance xylene-free tissue-clearing agent for routine histology: Preliminary histomorphological results

After the discovery of the hazardous effects of xylene, less toxic substitutes were proposed for routine histology in the last years. However, the introduction of new xylene-free substitutes in histological processes requires a careful evaluation of their performance in terms of morphological and microscopic details to permit a solid diagnosis as well as good quality immunohistochemical and biomolecular analyses. In this study, we analyzed the performance of a new commercially available xylene-free Tissue-Tek® Tissue-Clear® agent in comparison with another routine xylene-free solvent yet available and employed in routine histological process. Serial histological tissue samples (n = 300) were selected and processed with the two clearing agents. Comparison and evaluation were also performed on slides obtained 6 months after paraffin embedding and archive storage. Blinded semiquantitative analysis of technical performance and morphological details, including tissue architecture and nuclear and cytoplasmic details, was performed on Haematoxylin-Eosin stained sections by two technicians and two pathologists, respectively. Evaluation of tissue slides documented a good overall histological performance in slides obtained after processing with the two different clearing agents. Slides obtained with Tissue-Tek® Tissue-Clear® displayed a higher score in some quality parameters, further supporting its use as a valid alternative to the other commercial routine xylene-free solvents.