Microtomy: Cutting Formalin-Fixed, Paraffin-Embedded Sections.

Formalin-fixed, paraffin-embedded tissue (FFPE) still plays an important role in biobanking, since it is comparatively easy to obtain and store in comparison to fresh frozen tissue. They are stored as paraffin or FFPE blocks. Unstained slides derived from FFPE blocks may be used for hematoxylin and eosin histology, special stains, immunohistochemistry, and chromogenic or fluorescent in situ hybridization. In addition, tissue scraped off FFPE slides or from scrolls of FFPE tissue may be used for molecular or proteomic analyses. Hematoxylin and eosin staining of FFPE sections reviewed by a pathologist are highly valuable to ensure the presence of adequate lesional cells for molecular and other analyses. Therefore, proper microtomy technique is essential in the preparation of formalin-fixed, paraffin-embedded tissue for biobanking purposes. Here we describe the process of cutting paraffin embedded sections using a rotary microtome. We also highlight the possible pitfalls that may arise and discuss how to avoid them.