FFPE stands for "Formalin-Fixed Paraffin-Embedded" and describes the two main features of this method for tissue preservation. Formaldehyde is a formaldehyde solution and has been used since German physician Ferdinand Bloom discovered the preservative effect of formaldehyde in the late 19th century.
Paraffin is introduced into the network after fixation with formaldehyde, and the network is also surrounded by a paraffin shell to aid and prevent oxidation. Professionally fixed and embedded FFPE samples and the biomolecules they contain are relatively stable at room temperature.
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Fixed and embedded tissues are structurally stable and can be used almost indefinitely for microscopic anatomical examinations. However, over time, the antigenicity of some proteins deteriorates, limiting IHC studies to samples that are no longer than a few decades.
Double-stranded DNA is found to be stable in the FFPE block, but other, less stable biomolecules such as RNA can degrade within a decade or less, particularly after the section has been cut.
Archives in which a large number of FFPE samples are collected are a very extensive source of data when comparing many cases (i.e. FFPE samples from multiple donors) in order to draw statistically stable conclusions about the characteristics of a particular indication.
If the FFPE sample is to be used in high-risk biomedical research, it is important that every stage of the preparation process is carried out by a trained and certified professional, preferably a CLIA certified or a GAP accredited (College) of American Pathologists) Laboratory.