FFPE tissue sections are systematically reserved at ambient temperature in pathology departments for histology staining, immunohistochemistry, and in situ hybridization. The specimens are also used to detect mutations and for test for gene expression. The RNA degradation and modifications in the process of formalin fixation, as well as further deterioration that could be experienced during storage, reduce the value of these samples for molecular analysis that is quantitative.
However, this investigation was developed to study the effects of storage temperatures and time on the quality of FFPE samples by analyzing the RNA extracted from well-studied paraffin-embedded cells. You can also go to https://geneticistinc.com/blog/storing-ffpe-blocks to know about ffpe block storage in more brief.
Before a doctor can look at the tissue for diagnosis, the tissue must be prepared and then made into slides that can be used for observation.
The fixation of tissue is the primary stage in preparing the tissue to be used in the microscope slide. The reason for this procedure is to avoid the destruction of the tissue. When the tissue is collected, it needs to be placed in an adhesive like formalin. After 24 to 48 hours the tissue will be repaired and ready for another step.
The first stage of tissue processing is dehydration. The tissue gets immersed with increasing levels of alcohol to ensure that formalin and water can be eliminated. The tissue is then washed with an organic solvent in order to eliminate any alcohol, and then the tissues are prepared for embedding. The embedding process takes place when the specimen of tissue is encased with molten paraffin wax in order to create a formalin-fixed paraffin-embedded (FFPE) block. After the block has cured and is dry, the block is prepared for cutting.