Morphologic Manifestations of Toxic Cell Injury

Whatever causes injury to a cell-toxicant, toxin, infectious agent, or otherwise-the result is a simple or complex biochemical shift that generally results in a morphologic change, which can be observed in some form. The pathologist must be able to recognize that such changes in morphology reflect a significant alteration in the cell's homeostasis and then must decide whether or not this finding indicates reversible injury, irreversible injury, or adaptation to the new situation. Visible manifestations of disrupted function, whether ultrastructural, microscopic, or macroscopic, are lesions by definition, and lesions are still the primary means by which a toxicologic pathologist arrives at a diagnosis, hopefully one that includes the etiology as well as a description of the underlying morphologic alterations and a plausible pathogenesis of how the lesions came about. This chapter serves as an overview of the basic histologic and ultrastructural features that reflect cell injury and cell death as well as the sequelae to such processes.