The new optical criterion for objective diagnosis of malignant tumors in human beings and animals tissues is suggested. The molecules of NLC thin layers on sections of malignant tissues have a homeotropic orientation, while on the surface of benign and normal tissues the orientation is almost planar or tilted. Therefore malignant tumors in light microscope with crossed polarizer and analyzer always looks black. The different orientation of NLC molecules is explained by two orders different value of anchoring energy on the surface of malignant and benign tissues. The experiments on contact angles measurement of NLC and H2O droplets on investigated surfaces proved the difference in their surface tension that also confirm authenticity of a new criterion for microscopic malignancies' identification.