1. A system for determining biomarker concentrations in a tissue mass, the system comprising: an instrument for inserting into the tissue mass; a fiber optic probe for interfacing the tissue mass upon being inserted into the instrument and measuring turbid spectral data of the tissue mass, wherein measuring the turbid spectral data includes conducting fluorescence spectral measurements and diffuse reflectance measurements of the tissue mass simultaneously, wherein the fiber optic probe is a forward firing fiber optic probe that includes a probe tip comprising a plurality of centrally grouped illumination fibers that are concentrically surrounded by a plurality of collection fiber rings, wherein each of the collection fiber rings consists of a plurality of ring-specific collection fibers or a plurality of ring-specific collection fibers and a plurality of dead fibers; and a processing unit for converting the turbid spectral data to absorption, scattering, and intrinsic fluorescence spectral data via a Monte Carlo algorithm or a diffusion algorithm and quantifying biomarker concentrations in the tissue mass using the absorption, scattering, and intrinsic fluorescence spectral data, wherein the intrinsic fluorescence spectral data is corrected to account for the absorption and scattering data.