by in vivo multiphoton microscopy Distinguishing between benign and malignant melanocytic nevi

Monitoring of atypical nevi is an important step in early detection of melanoma, a clinical imperative in preventing the disease progression. Current standard diagnosis is based on biopsy and histopathological examination, a method that is invasive and highly dependent upon the physician’s experience. In this work, we employed a clinical multiphoton microscope to image in vivo and non-invasively melanocytic nevi at three different stages: common nevi without dysplastic changes, dysplastic nevi with structural and architectural atypia, and melanoma. We analyzed multiphoton microscopy (MPM) images corresponding to 15 lesions (5 in each group) both qualitatively and quantitatively. For the qualitative analysis, we identified the morphological features characteristic of each group. MPM images corresponding to dysplastic nevi and melanoma were compared with standard histopathology in order to determine correlations between tissue constituents and morphology and to evaluate whether standard histopathology criteria can be identified in the MPM images. Prominent qualitative correlations included the morphology of epidermal keratinocytes, the appearance of nests of nevus cells surrounded by collagen fibers, and the structure of the epidermal-dermal junction. For the quantitative analysis, we defined a numerical “multiphoton melanoma index (MMI)” based on 3D in vivo image analysis that scores signals derived from two-photon excited fluorescence, second harmonic generation, and melanocyte morphology features on a continuous 9-point scale. Indices corresponding to common nevi (0–1), dysplastic nevi (1-4) and melanoma (5-8) were significantly different (p<0.05), suggesting the potential of the method to distinguish between melanocytic nevi in vivo. on April 2, 2014. © 2014 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Author Manuscript Published OnlineFirst on March 31, 2014; DOI: 10.1158/0008-5472.CAN-13-2582