Nonlinear microscopy of eumelanin and pheomelanin with sub-cellular resolution

Pump-probe microscopy non-destructively differentiates eumelanin and pheomelanin and can be used to quantify melanin distributions in thin biopsy slices. Here we have extended that work for imaging eumelanin and pheomelanin distributions on a sub-cellular scale, allowing elucidation of characteristics of different cell types. The results show that melanin heterogeneity, previously found to be characteristic of melanomas, persists on the sub-cellular scale. We have also found spectral changes associated with melanin located in melanophages, which could potentially differentiate invasive pigmented melanocytes from melanophages without immunohistochemical staining.