A brief review of modern toxicologic pathology in regulatory and explanatory toxicity studies of chemicals.

Macroscopic and histologic evaluation of animal studies for general toxicity and carcinogenicity are cornerstones of the risk assessment of new chemical entities. Standard toxicopathologic evaluation is mainly based on the study of paraffin sections stained with hematoxylin and eosin. There are, however, a number of new approaches and techniques which have improved the objectivity of evaluation and the accuracy of cell identification, and provided deeper insight into the molecular biological mechanisms of toxicity and carcinogenicity. Such approaches include the standardization of the nomenclature, the creation of data banks for morphological alterations, the use of computers to register pathological findings in toxicity studies and to statistically evaluate incidences, and the use of morphometry. Other modern techniques are immunohistochemistry, in situ hybridization, and the assessment of cell kinetics.