Nonleukemic Lymphocytosis I f 3 



makes the peripheral blood smear in infectious mononucleosis characteristic 

 if not diagnostic. In diseases other than infectious mononucleosis, virocytes 

 seldom make up more than 15 per cent of the leukocytes. It is also true 

 that the virocytes seen in conditions other than infectious mononucleosis 

 usually have the appearance of the cells described by Downey as Type 3. 



Fig. 11-5. Herpes zoster, peripheral blood. Wright's stain, (x 170(1) 



However, the classification as to the type of virocyte in infectious mono- 

 nucleosis has little significance since a rather rapid transition can be ob- 

 served from one type to another if serial peripheral blood smears are 

 examined. On morphologic grounds alone, then, the atypical lymphocytes 

 seen in the peripheral blood in the conditions listed in Subgroup I -A are 

 very similar and for this reason it seems justified to call them "virocytes" 

 and to abandon the use of the term "infectious mononucleosis cell." 



It might be said that since the diagnosis of infectious mononucleosis can 

 be substantiated by serologic studies, 3 these morphologic observations are 

 not particularly disturbing. This is only partially true. In the first place the 

 presence of virocytes can often be of great assistance in suspecting the diag- 

 nosis in diseases such as infectious hepatitis or viral pneumonitis when the 



