Living pancreatic cancer tissues grown subcutaneously in nude mice are studied by in vivo microscope Raman spectroscopy. Comparing the spectra of living pancreatic cancer tissue to that of the dead same tissue, it is found that they are different each other. In the subtraction spectrum, Raman bands observed at 937, 1251, 1447 and 1671 cm-1 are appeared in negative direction and those observed at 966 and 1045 cm-1 are appeared in positive direction. The results strongly suggest that the spectral changes reflect the protein conformational changes in the tumor tissue with death of the host animal. The present result demonstrates the importance of in vivo, real time studies of biomedical tissues using Raman spectroscopy.