In vivo imaging of pigmented lesions in human skin was performed with a clinical multiphoton microscopy (MPM)-based tomograph (MPTflex, JenLab, Germany). Two-photon excited fluorescence was used for visualizing endogenous fluorophores such as NADH/FAD, keratin, melanin in the epidermal cells and elastin fibers in the dermis. Collagen fibers were imaged by second harmonic generation. Our study involved in vivo imaging of benign melanocytic nevi,
atypical nevi and melanoma. The goal of this preliminary study was to identify in vivo the characteristic features and
their frequency in pigmented lesions at different stages (benign, atypical and malignant) and to evaluate the ability of in
vivo MPM to distinguish atypical nevi from melanoma. Comparison with histopathology was performed for the biopsied
lesions. Benign melanocytic nevi were characterized by the presence of nevus cell nests at the epidermal-dermal
junction. In atypical nevi, features such as lentiginous hyperplasia, acanthosis and architectural disorder were imaged.
Cytological atypia was present in all the melanoma lesions imaged, showing the strongest correlation with malignancy. The MPM images demonstrated very good correlation with corresponding histological images, suggesting that MPM
could be a promising tool for in vivo non-invasive pigmented lesion diagnosis, particularly distinguishing atypical nevi