Elemental Analysis of FFPE Tissue Blocks: Overcoming Paraffin Embedding Challenges with EDXRF Spectroscopy

Tissue specimens processed as Formalin-Fixed Paraffin-Embedded (FFPE) blocks are routinely collected during interventions for diagnostic purposes and stored for archival purposes. However, the elemental composition of these FFPE tissue samples remains largely unexplored due to the lack of suitable analytical tools. This study aimed to address this gap by investigating the elemental composition of FFPE tissue samples using Energy-Dispersive X-ray Fluorescence (EDXRF) spectroscopy. A total of 18 sets of mirrored tissue samples, processed either as pellets or FFPE blocks, were analyzed to develop calibration curves and assess the influence of paraffin embedding on elemental peak intensities (specifically S, Ca, Fe, Cu, and Zn) in the EDXRF spectrum. An additional set of samples was used for validation by comparing the intensity obtained from FFPE tissue blocks to that obtained from pellets (considered the true value). Our results demonstrate that the intensities obtained using this procedure exhibit a bias towards the true value of less than 9% for all elements analyzed. Furthermore, after applying calibration curves using the External Calibration Method, the concentrations of S, Ca, Fe, Cu, and Zn obtained from FFPE and pellet samples were not statistically different. These findings highlight the feasibility and accuracy of using EDXRF spectroscopy for elemental analysis of FFPE tissue samples, overcoming the limitations posed by the paraffin embedding process. This study contributes valuable insights into the elemental composition of FFPE tissue samples and paves the way for further research in biomedical and clinical applications.