The diagnosis of cytomegalovirus (CMV) in tissue sections is usually quite easy because of the characteristic appearance of intranuclear inclusions. At times the morphological features are equivocal, the nuclear findings may be atypical or only a single cell may be affected, thereby creating uncertainty about the diagnosis. This report reviews our experience with the various microscopic techniques that can be used to make definitive identification of CMV.
EM - Visualizing the viral particles in a single or even lysed cell by routine electron microscopy can make the definite diagnosis, but section size limits the usefulness in the detection of early CMV infection (fig. 1). However, if a diagnosis can not be made with certainty by the following methods, EM can be performed on stained paraffin sections for confirmation.
H&E - A Hematoxylin & Eosin stain that discloses characteristic intranuclear inclusions surrounded
by a clear halo indicates CMV infection (fig.2A).