Pitfalls in the diagnosis of herpes simplex infection in respiratory cytology

Objective To evaluate the prevalence and potential pitfalls in making an accurate diagnosis of respiratory berpetic infection. Study Design Eighteen case. with the diagnosis of herpes simplex virus (HSV) infection were identified from a total of 7,501 (0.24%) respiratory specimens. All case. were evaluated for classic cytomorphologic features of HSV infection and associated cytologic findings. The parameters studied included number of cells with HSV cytopathic effect, intranuclear inclusions, multinucleation, presence of atypical squamous cells, reparative changes, presence and decree of inflammation and associated obscuring factors. Results Only a minority of cases (28%) had numerous cells with classic viral cytopathic change. Four (22%) of 18 cases showed atypical squamms cells, and 5 (28%) revealed reparative changes. The majority of the cases were associated with inflammation, which was severe in 4 cases (22%). Blood and degenerative changes obscured the cytologic findings in 3 cases (17%). One rase shoved a necrotic background. Conclusion Due to the low prevalence of HSV infection in respiratory cytology, a high index of suspicion is neccessary for an HSV diagnosis. Pitfalls for a false negative diagnosis include limited number of cells with viral cytopathic change, only mononuclear cells with viral changes and obscuring inflammation or blood. Pitfalls for a false positive diagnosis of malignancy include atypical keratinized sqliamous cells, atypical repair cellular degeneration and necrotic background.