'Upcycling pathology': targeted next-generation sequencing is feasible in re-purposed haematoxylin and eosin and immunostained formalin-fixed paraffin-embedded sections in lung cancer biopsies.

Lung cancers are often diagnosed on small biopsy formalin-fixed paraffin-embedded (FFPE) material. Despite judicious selection of diagnostic immunohistochemistry studies and the use of tissue conservation workflows, biopsy material can be limited in some cases, necessitating re-biopsy for the purpose of downstream predictive molecular marker testing. The aim of this study is to investigate the feasibility of an alternative method to re-biopsy: that of re-purposing material from diagnostic slides for molecular testing. Forty lung cancer biopsy specimens were selected. After digital archival of the diagnostic slides, material from haematoxylin-and-eosin-stained (H&E-stained) and immunostained FFPE tissue sections was sent for deoxyribonucleic acid (DNA) extraction, followed by targeted next-generation sequencing (NGS). While the extracted DNA was of sub-optimal to poor quality, we obtained sequencing results for 33 of 40 cases (82.5%), with full concordance of detected variants observed in 30 cases and partial concordance observed in the remaining three cases. We conclude that it is feasible to re-purpose diagnostic H&E-stained and immunostained FFPE sections for targeted NGS testing. Our results serve as a starting point for further validation and refinement of this workflow.