Specific Methods for Detection and Quantification of Apoptosis in Tissue Sections

Apoptosis as a distinct pathologic process has been recognized for decades. Its importance in many disease processes has become increasingly appreciated as new techniques for detecting and quantifying it have been developed with almost exponential rapidity. While all these techniques have their advantages and disadvantages, it is surprising how often simple morphologic assessment is overlooked in the rush to develop ever more sophisticated and “glitzy” techniques. With the appropriate training, apoptosis can be evaluated and even semi-quantified by simply examining a standard hematoxylin-and eosin-stained section closely and carefully. Admittedly, apoptosis (also termed apoptotic necrosis) can be harder to detect morphologically than necrosis (also termed oncotic necrosis). Its rapid progression once triggered (usually minutes), the rapid disposition of the apoptotic cells via ingestion by adjacent cells or resident macrophages (often just several hours), and the participation of only small numbers of cells at any one time during the process can make detecting apoptosis challenging. However, there are unique morphologic features associated with the process that an experienced morphologist can easily and rapidly detect to obtain a “global,” if not truly quantitative assessment of the degree of apoptosis occurring in a particular tissue. Simple morphologic assessment offers the advantages of giving the investigator an idea of the distribution of apoptosis within a tissue in the context of “real life” as well as the specific cell types involved within that tissue.