The polymerase chain reaction. Method and applications in dermatopathology.

Since it was first reported in 1985, the polymerase chain reaction (PCR) has revolutionized the way molecular studies are performed, and has developed into one of the most powerful tools in molecular pathology. By use of a cyclic change of temperature, a specific and exponential in vitro amplification of a target DNA sequence can be achieved within hours. As a template for PCR reactions, total genomic DNA is used; this can be readily extracted from clinical specimens. Very low quantities of DNA, as well as DNA degraded by fixation, can also be used as a template for PCR reactions, allowing formalin-fixed, paraffin-embedded tissue to become amenable to detailed molecular analysis. Sequences specific for certain viruses and other microorganisms, as well as molecular marker sequences associated with various types of human cancer, can be readily detected in paraffin-embedded tissue sections. The methodology of PCR, along with various applications in dermatopathology, are reviewed.