Tzanck test
Synonyms and keywords: Tzanck smear, Chickenpox skin test, herpes skin test

# Overview
In dermatopathology, the Tzanck test, also Tzanck smear, is scraping of an ulcer base to look for Tzanck cells.  It is sometimes also called the Chickenpox skin test and the herpes skin test. The test is named after Arnault Tzanck (1886-1954), a Russian dermatologist. Atypical Tzanck cell is a large round keratinocyte with a hypertrophic nucleus, hazy or absent nucleoli, and abundant basophilic cytoplasm. The basophilic staining is deeper peripherally on the cell membrane due to the cytoplasm's tendency to get condensed at the periphery, leading to a perinuclear halo. Tzanck cells commonly are found in: herpes simplex, varicella, herpes zoster and pemphigus vulgaris.

# Historical Perspective
- Diagnostic cytology is the study of individual cells and their characteristics and functions.
- George Papanicolaou is considered the father of exfoliative cytology.
- Cytology technique was first used by Tzanck for the diagnosis dermatological disorders such as herpes and other vesico-bullous lesions.
- The test is named after Arnault Tzanck (1886-1954), a Russian dermatologist.
- The different techniques of cytological studies include aspiration cytology, imprint smear, exudate smear, skin scraping smear, and Tzanck smear.

# Tzanck Smear

## Sample Collection
- In patients with suspected viral lesions the sample must be collected from fresh vesicular lesions rather than the healing crusted lesions, to have a sample with adequate number of virus infected cells.
- The vesicle should be un-roofed and the base of the ulcer must be scraped with a scalpel or with a scapula.
- The obtained material should be then transferred on to a clean glass slide.
- Care should should be taken that the glass slide is clean and has no finger prints as the specimen will not stay on the glass slide with finger prints.

## Fixation of the Smear
- A fixative fluid contains reactive chemicals and is useful for the preservation of the specimens. The fixative fluid prevents the denaturation of the proteins and autolysis and helps in maintaining the cellular morphology and its contents.
- Fixatives usually contain chemicals like formalin, glutaraldehyde, methanol, ethanol, acetone, acetic acid, chromates, and picric acid.
- Once the sample is transferred on to the glass slide it should be fixed immediately using a fixative fluid to prevent drying of the tissue.

## Staining of the Smear
- Many stains can be used for the fixation of the Tzanck smear must the most commonly used stain is the Giemsa stain.
- Other stains that can be used include the following:
Hematoxylin and eosin
Wright's stain
Methylene blue
Papanicolaou
Toluidine blue
- Hematoxylin and eosin
- Wright's stain
- Methylene blue
- Papanicolaou
- Toluidine blue

## Tzanck Smear Findings
- A typical Tzanck cell is a large round keratinocyte with a hypertrophic nucleus, hazy or absent nucleoli, and abundant basophilic cytoplasm. The basophilic staining is deeper peripherally on the cell membrane due to the cytoplasm's tendency to get condensed at the periphery, leading to a perinuclear halo.
The following are the list of cutaneous diseases which can be differentiated based on the findings on the Tzanck smear: