[Polymerase chain reaction in diagnostic pathology].
DNA is a very stable molecule and fixation as well as routine histological processing does not destroy its molecular structure. Hence the possibility exists to use this material for molecular genetic analyses. The polymerase chain reaction (PCR) opens the chance to amplify DNA to huge amounts from pathological paraffin and plastic blocks and to use this DNA for further examinations, such as detection of mutations or translocations in malignant tumors, e.g. t(14;18) in follicular lymphomas, bcr/abl in chronic myeloic leukemia, t(11;22) in Ewing sarcomas or of the ras-gene in colon cancer, overexpression of tumor related mRNA, e.g. mdr1-mRNA of the multidrug associated P-Glycoprotein, or detection of foreign DNA from viruses or bacteriae, as well as analysis of hereditary diseases. PCR in its various forms (conventional PCR, PCR with direct sequencing, reverse transcriptase (RT)-PCR, nested primer PCR, quantitative RT-PCR, inverse PCR, degenerated primer (DOP) PCR, in situ PCR, in situ RT-PCR etc.) has proven to supplement routine diagnostic work in many occasions, however, it has to be emphasized that up to now there exists no example for a complete replacement of histological or immunhistological examination by PCR. As consequence, histology remains the first and most important step towards a relevant diagnosis supplemented e.g. by PCR and other techniques of molecular biology.