Pathology

Transfer of molecular genetic technology and knowledge from the research to the diagnostic laboratory is giving the pathologist new, powerful tools to diagnose and monitor disease. The most immediate application is the use of nucleic acid probes to detect viral genomic material in cytological smears or microscopic sections by in situ hybridization.¹ Hybridization either with a radioactive recombinant DNA or RNA for autoradiography or with a nonradioactively labeled nucleic acid to produce a visible product now can be performed with commercially available reagents. This identifies genomic sequences of adenoviruses, BK and JC viruses (human polyomavirus), cytomegalovirus, herpes simplex virus-1 and -2, Epstein-Barr virus, human immunodeficiency virus, human T-cell lymphotropic virus type I, hepatitis A and B viruses, and human papillomaviruses. Unfortunately, in situ hybridization is still relatively insensitive since 100 to 200 genomic copies or more are needed in a single cell for detection so that negative or equivocal