10 – Special Techniques in Toxicologic Pathology

This chapter deals with the special techniques used in toxicologic pathology. Advances in cell and molecular biology have engendered a wide range of techniques that can be used to augment traditional morphologic tools to investigate mechanisms of disease or toxicity. In the team-oriented scientific world today, pathologists must be familiar with the technical basis and utility of a large variety of the techniques, some of which are slide based and some of which are solution based. In solution-based assays, the tissue is homogenized and DNA, RNA, or protein is extracted for analysis. In contrast, slide-based techniques, such as immunehistochemistry, in situ hybridization; in situ polymerase chain reaction (PCR); and laser capture microscopy, retain the tissue architecture and thus, have the common ability to provide spatial localization of alterations in DNA, RNA, or protein at the cellular level in a heterogeneous cellular population, e.g., tissue. Slide-based techniques in particular reside more commonly in the pathology laboratory and require interpretation of the slide by a trained pathologist. This chapter focuses on some of the special techniques that a toxicologic pathologist utilizes and the potential applications and limitations of each technique.