A method and system to differentiate a tissue margins during various medical procedures. A region containing a biological tissue is irradiated, with a substantially monochromatic light. Raman spectroscopic data is obtained from the irradiated region. A boundary between a neoplastic portion and a non-neoplastic portion, in the region containing the biological tissue, is differentiated by evaluating the Raman spectroscopic data for at least one Raman spectroscopic value characteristic of either the neoplastic portion or the non-neoplastic portion. The neoplastic portion is selected for physical manipulation based on the differentiation of the boundary between the neoplastic portion and the non-neoplastic portion.