Keratinocyte morphology of human skin evaluated by in vivo multiphoton laser tomography.

BACKGROUND: Multiphoton tomography (MPT) is a novel non-invasive imaging method in dermatology allowing the depiction of the epidermis with sub-cellular resolution. Here, we present a descriptive characterization of unaffected human epidermis, morphometric data on human keratinocytes and some epidermal parameters in vivo and a morphological characterization of keratinocyte changes in actinic keratoses. METHODS: In a clinical setting, 57 volunteers of different age groups were examined using MPT. RESULTS: The morphological appearance of keratinocytes showed polygonal cells in the horny layer, a granular cytoplasm in the stratum granulosum, smaller prickle cells in the stratum spinosum and hyperpigmented small round basal cells. Actinic keratoses presented remarkable differences including widened inter-cellular spaces, heterogeneity in cellular fluorescence and shape as well as an increased ratio of nuclear to cellular size. Finally, the thickness of the epidermis was significantly increased in actinic keratoses compared with the control. CONCLUSION: In vivo MPT provides high-resolution images allowing the identification and quantification of cellular morphometric parameters. First observations of morphology and morphometry of actinic keratoses are reported.