Xylene versus Isopropanol for Paraffin Wax Processing of Lung Tissue

The microscopic observation of lung tissue is challenging due to its fragile nature. Xylene and isopropanol are common tissue-clearing reagents used before paraffin embedding, yet no studies have compared these two reagents in lung tissue processing. Due to the well-known health risks xylene could introduce to operators, as well as its environmental hazards, it has long been desired that a less harmful alternative to xylene with the same staining effects be introduced. Thus, we systematically assessed the efficacy of isopropanol as a substitution for xylene. Lung tissue obtained from diseased donors and explanted lungs from recipients were processed simultaneously using either xylene or isopropanol prior to paraffin embedding. Scoring of the overall staining quality after H&E staining, along with the ease of sectioning, was compared systematically. Fluorescent staining was performed to explore alveolar morphology and the overall lectin fluorescence signal between groups. To understand differences in antibody staining, the signal-to-noise ratio (SNR) of smooth muscle actin (SMA) and elastin was examined. No difference was observed with regard to ease of sectioning, staining quality, alveolar circularity, alveolar wall thickness or the SNR between slides processed with xylene or isopropanol. This study demonstrated comparable outcomes of isopropanol and xylene in lung tissue processing, suggesting isopropanol as a more favorable, operator- and environment-friendly substitute for xylene with regards to tissue processing.