The subject matter described herein includes an optical assay system for intraoperative assessment of tumor margins. According to one aspect, the subject matter described herein includes a biological sample containment and illumination apparatus for holding a biological sample for illumination by a plurality of electromagnetic radiation probes. The biological sample containment and illumination apparatus includes a plurality of frame members positioned with respect to each other to form an interior space for receiving a biological sample. At least one of the plurality of frame members includes a plurality of probe receiving locations for receiving a plurality of electromagnetic radiation probes. The probe receiving locations position the probes with respect to the biological sample to allow illumination of plural locations of the biological sample by the probes.