1. A method of using a spectral mask to process spectral data, the method comprising the steps of: (a) applying at least one spectral mask to identify a subset of spectral data obtained from a plurality of regions of a tissue sample, wherein said subset comprises data that are non-representative of a zone of interest of said tissue sample; (b) identifying one or more regions of said tissue sample from which said subset was obtained; and (c) processing spectral data obtained from said plurality of regions in a tissue classification scheme.