Human normal colon mucosa and colon cancer tissue were studied using the time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and principal component analysis (PCA) techniques. The surfaces of the tissues were successfully cleaned by C-60(2+) cluster-ion beams before the ToF-SIMS images were obtained. A PCA on the spectra and images were performed to compare differences in the peaks and images of normal and cancer tissues. Significant differences in principal component 1 (PC 1) score values for normal and cancer tissues were observed, and each PC 1 loadings had a specific peak pro. le of proteins. In addition, the PC images obtained from the ToF-SIMS images for normal and cancer tissues were clearly distinguishable, and the amino acid fragments associated with normal and cancer tissues were found to have originated from the lamina propria region and the epithelium cells, respectively. Based on the PCA results, structural distortion of the crypts in the cancer colon tissue could be attributed to the proliferation of the cancerous epithelium cells. This work shows that the application of the ToF-SIMS imaging technique with PCA could be a useful method of obtaining valuable information for cancer analysis. (c) 2008 Elsevier B.V. All rights reserved.