Tumor cells are morphologically different from normal cells. In this situation, we proposed that plectin, one of the intermediate filament associated proteins, might play some special roles in the tumorigenesis. Plectin exhibits a wide distribution spectrum among various tissues; however, it is scarcely investigated in tumor tissues including colorectal adenocarcinoma. In this study, we searched the plectin expression in 25 cases of colorectal adenocarcinoma and 10 cases of tubular adenoma with focal adenocarcinoma by immunohistochemical method. The results reveal that plectin is up-regulated in colorectal adenocarcinoma as well as in bizarre glands and locally invasive tumor nests in tubular adenoma, compared with normal colorectal mucosa. Over-expression of plectin in locally invasive tumor nests might help us in diagnosis of distinguish microinvasive foci from normal glands. The bizarre glands in adenoma might be precancerous lesions since the expression of plectin in them was identical to that of adenocarcinoma but in contrast to that of normal glands. The overexpression of plectin might affect the organization of cytoskeleton, which might further cause tumorigenesis and morphological change of colorectal epithelial cells.