We have developed a portable, breast margin assessment probe leveraging diffuse optical spectroscopy to quantify the morphological landscape of breast tumor margins during breast conserving surgery. The approach presented here leverages a custom-made 16-channel annular photodiode imaging array (arranged in a 4×4 grid), a raster-scanning imaging platform with precision pressure control, and compressive sensing with an optimized set of eight wavelengths in the visible spectral range. A scalable Monte-Carlo-based inverse model is used to generate optical property [μs′(λ) and μa(λ)] measures for each of the 16 simultaneously captured diffuse reflectance spectra. Subpixel sampling (0.75 mm) is achieved through incremental x, y raster scanning of the imaging probe, providing detailed optical parameter maps of breast margins over a 2×2 cm2 area in ∼9 min. The morphological landscape of a tumor margin is characterized using optical surrogates for the fat to fibroglandular content ratio, which has demonstrated diagnostic utility in delineating tissue subtypes in the breast.