We investigate optical signatures of normal and cancer tissues by measuring nine cases of oral squamous cell carcinomas transplanted into tongue of nude mice. Transmission results were measured with a spatially translated fiber probe for auto-fluorescence spectra of normal and cancer specimens in 450-750 nm. Normal and cancer specimens were quantitatively compared based on extinction coefficients (mu(t)) calculated by collimated transmission method. Although direct comparison of mu(t) may be difficult to detect cancer specimens, it was found that use of multiple determinants based on spatial variance and a spectral ratio of mu(t) shows promise for the diagnosis. The preliminary results attest the feasibility and challenges of screening precancerous oral tissues using optical detection. (C) 2009 Elsevier B.V. All rights reserved.