Tzanck smear: a useful diagnostic tool.

Diagnostic cytology is a relatively new science. Cytology (Greek word: kytos = hollow vessel) is the study of individual cells and their intrinsic characteristics and functions. George Papanicolaou is considered the father of exfoliative cytology, but cytology was first used in cutaneous disorders by Tzanck in 1947, for the diagnosis of vesiculo-bullous disorders, particularly herpes simplex. Since then cytology has been widely used by dermatologists for diagnosing various cutaneous dermatoses. Cytodiagnosis is very simple, rapid, cheap and reliable. Its various methods are aspiration cytology, imprint smear, exudate smear, skin scraping smear, and Tzanck smear. Some practical applications of Tzanck smear in dermatological practice are summarized in Table 1. Cytological diagnosis of tumors is not commonly used because surgical excision and biopsy are easy to perform. In some diseases, cytological findings are diagnostic, while in others they are only suggestive of a disease and need to be confirmed by histology.