Dermatoscopy versus Tzanck smear test: a comparison of the value of two tests in the diagnosis of pigmented skin lesions.

Background: Dermatoscopy is the most commonly used noninvasive tool for the diagnosis of pigmented skin lesions, but few studies have investigated the value of cytology in the identification of those lesions.

Objective: We compared the accuracy of dermatoscopy with that of the Tzanck smear test in the diagnosis of pigmented skin lesions, and in differentiating melanocytic from nonmelanocytic lesions.

Methods: Two dermatologists used either dermatoscopy or the Tzanck smear test to evaluate pigmented skin lesions, and the diagnostic accuracy of those methods was determined.

Results: Two hundred pigmented skin lesions (110 melanocytic and 90 nonmelanocytic) were evaluated. Cytology was superior to dermatoscopy in differentiating melanocytic pigmented lesions from nonmelanocytic pigmented lesions, but the overall diagnostic accuracy of those methods was the same (90.5%) for all lesions. The diagnostic accuracy of the Tzanck smear test was higher than that of dermatoscopy for both melanocytic and nonmelanocytic malignant pigmented lesions; however, those differences were not significant.

Limitations: Pigmented skin lesions were not evaluated by a dermatologist who used a combination of dermatoscopy and the Tzanck smear test. No conclusion was made about the reliability of those two methods or whether the experience of the dermatologist affected the results. Immunohistochemical staining of the cytologic samples was not performed.

Conclusion: The diagnostic accuracy of the Tzanck smear test in assessing pigmented skin lesions is similar to that of dermatoscopy. The Tzanck smear test may be a useful diagnostic adjunct to dermatoscopy for determining the melanocytic or nonmelanocytic origin of certain pigmented skin lesions.