Utility of Confocal Laser Scanning Microscopy (CLSM): With Reference to Interpretation in Immunostaining

Abstract

Immunohistochemistry is a useful diagnostic procedure in routine pathological practice including cytology. However, when occasional discrepancy between cytological immunostaining and histological immunostaining in the intracellular localization of a positive reaction is encountered, we tend to think that the discrepancy is due to differences in the fixation agents and staining processes for these two methods. As a demonstrable example of such a discrepancy, glucose transporter-1 (GLUT-1) staining profiles in cytological specimen and histological specimen are presented. GLUT-1 overexpression is usually considered to be predominant on the cell membrane, based on the function of GLUT-1 involved in the effective transportation of glucose, but GLUT-1 is observed in the cytoplasm more often than expected. Especially in cytological specimens, localization of GLUT-1 expression is occasionally difficult to recognize because of ill-defined cell cluster structure and marked stratification. The interpretation may result in a pitfall: the staining pattern basically differs from that in the histological specimen. Confocal laser scanning microscopy (CLSM) is easily applied to usual cytological immunostaining and histological immunostaining colorized by diaminobenzidine as well as Papanicolau-stained and hematoxylin & eosin-stained specimens without specific or tedious pretreatment. Observation of immunohistochemical specimens using CLSM is very helpful in accurate interpretation of the immunolocalization especially because the cytoplasm-predominant expression of the immunoreaction often assumes a seemingly membrane-predominant pattern in cytological specimens.