  Pump-probe microscopy of melanin in tumors has been proposed to improve
diagnosis of malignant melanoma, based on the hypothesis that aggressive
cancers disaggregate melanin structure. However, measured signals of melanin
are complex superpositions of multiple nonlinear processes, which makes
interpretation challenging. Polarization control during measurement and data
fitting is used to decompose signals of melanin into their underlying molecular
mechanisms. We then identify the molecular mechanisms that are most susceptible
to melanin disaggregation and derive false-coloring schemes to highlight these
processes in biological tissue. We exemplary demonstrate that false-colored
images of a small set of melanoma tumors correlate with clinical concern. More
generally, our systematic approach of decomposing pump-probe signals can be
applied to a multitude of different samples.
