[In situ gene amplification on tissue sections (in situ PCR). A new technique for pathologists].

In situ polymerase chain reaction is a recent technique which combines the sensitivity of PCR reaction to intracellular localization of genomic sequences with the same specificity as in situ hybridization. This reaction is based on the in situ annealing and polymerisation of oligonucleotides complementary to nucleotides located at each side of the target DNA sequence to amplify. We describe the Hot Start PCR (DNA) and the Hot Start PCR after reverse transcription step (RNA). It allows to amplify some nucleic sequences to a high level, becoming easier to detect. The vizualisation can be realized by direct in situ PCR, the product obtained being directly identifiable by incorporation of labeled nucleotides or primers, or preferentially by indirect in situ PCR. In this case, the amplification is followed by in situ hybridization with labeled probes. This last procedure is more specific. Numerous controls are essential at each step of the technique for validating results.