Frozen or paraffin sections ?
Some epitopes do not survive fixation and embedding. From the same frozen block you can get DNA, RNA, free nuclei for FISH or cell cycle analysis, protein and a stained section on serial sectioning From a paraffin block you can get DNA and RNA for PCR amplification (extensive crosslinking prevents extraction of long nucleotide stretches), free nuclei for ploidy and cell cycle analysis, cells for flow cytometry Ref and several section on serial sectioning. Fixation and embedding prevents degradation and physical relocation of antigen (protein, DNA, RNA) by crosslinking. Morphology on frozen is poor. Paraffin sections allow unlimited almost identical serial sections. Cell and tissue shrinkage, associated with fixation and embedding, results in higher antigen density on the section. Nasty bugs are destroyed by fixation Most of the specimens stained in a routine immunohistochemistry lab in Surgical Pathology are formalin-fixed, paraffin embedded tissues. Fixation and embedding cause antige
