Viral Infections (Cytomegalovirus, Herpesvirus, and Others)

Michael J. Thrall, MD

Key Facts

Cytopathology

Common lung viruses with identifiable cytopathic effect include CMV and herpesvirus
- CMV produces nuclear enlargement with a prominent intranuclear inclusion and marginated chromatin
- Herpesvirus shows the triad of multinucleation, margination, and molding
Other viruses that may involve lung and be identified by cytology include adenovirus, respiratory syncytial virus, and measles
- Consider other viruses when nuclear enlargement and homogenization are seen without typical CMV or herpes features

Top Differential Diagnoses

Nuclear changes due to inflammation or cytotoxic therapy may mimic viral cytopathic effect

(A) CMV infection produces classic Cowdry type A nuclear inclusions within a markedly enlarged nucleus

. This Pap-stained example has a typical red inclusion. (B) In some instances, such as in this ThinPrep containing CMV, the inclusion

may not stain red, but nuclear enlargement and homogenization aid recognition. (C) This example of herpesvirus in a Pap-stained smear shows the typical nuclear features of chromatin margination, multinucleation, and nuclear molding