What is FFPE?
FFPE stands for
Formalin-Fixed, Paraffin-Embedded. It is a widely used method in histology for the preservation of
biological tissues. This technique involves fixing the tissue in formalin to preserve the cellular architecture and proteins, followed by embedding it in paraffin wax to create solid blocks that can be easily sectioned for microscopic examination.
Fixation: The tissue is immersed in a formalin solution, usually 10% neutral-buffered formalin, for several hours to days. This step preserves the tissue by cross-linking proteins and preventing degradation.
Dehydration: The fixed tissue is then dehydrated through a series of graded alcohol baths, typically ethanol, to remove water content.
Clearing: The tissue is cleared using a solvent like xylene, which makes it easier for the paraffin to infiltrate the tissue.
Embedding: The cleared tissue is then infiltrated with molten paraffin wax and allowed to harden, forming a solid block.
Sectioning: Thin sections, usually 4-5 micrometers thick, are cut from the paraffin block using a microtome. These sections are then mounted on glass slides for staining and analysis.
Long-term preservation: Tissues preserved using FFPE can be stored for many years without significant degradation, making them valuable for retrospective studies.
Compatibility with various techniques: FFPE samples can be used for multiple downstream applications, including histological staining, IHC, and molecular assays like PCR and sequencing.
Cost-effective: The chemicals and equipment required for FFPE are relatively inexpensive, making it a cost-effective method for tissue preservation.
Potential for antigen masking: The cross-linking of proteins during fixation can mask antigens, making it challenging to perform certain IHC assays without antigen retrieval techniques.
DNA/RNA degradation: Although FFPE preserves tissue morphology well, the formalin fixation process can cause some degradation of DNA and RNA, which may affect molecular analyses.
Processing artifacts: Improper processing can lead to artifacts, such as tissue shrinkage or poor infiltration, which can compromise the quality of the tissue sections.
How is FFPE used in clinical diagnostics?
In clinical settings, FFPE is extensively used for the diagnosis of various diseases, including
cancer. Pathologists examine FFPE tissue sections under a microscope to identify abnormal cellular structures and patterns. Techniques like IHC are employed to detect specific proteins that may indicate the presence of malignancies or other pathological conditions. FFPE samples are also used in
genomic studies to identify genetic mutations and alterations that can guide treatment decisions.
How is FFPE used in research?
FFPE tissues are invaluable in research for studying
disease mechanisms, biomarker discovery, and
drug development. Researchers can access archived FFPE samples to study the molecular and genetic profiles of diseases over time. The ability to perform high-throughput analyses on FFPE samples has advanced our understanding of many diseases and facilitated the development of targeted therapies.
Conclusion
FFPE is a cornerstone technique in histology, providing a reliable method for the long-term preservation and analysis of biological tissues. Its applications in both clinical diagnostics and research have made it an indispensable tool in the field of medical science.
