Immunohistochemical localization of β-catenin in normal oral epithelium (a-c), oral leukoplakia without dysplasia (d-f), oral leukoplakia with mild dysplasia (g-i), oral leukoplakia with severe dysplasia (j-l), and oral squamous cell carcinoma (m-o). (a, d, g, j) Hematoxylin and eosin staining. (b, c, e, f, h, i, k, l, m-o) β-Catenin staining. (b, c) Signals were detected in the cell membrane of the basal and spinous layer, but not in the cytoplasm and nuclei. (e, f) Signals were detected in the cell membranes and cytoplasm. (h, i) Signals were detected in the cell membranes and nuclei. (j) The area for dysplasia is characterized by an increased nuclear-cytoplasmic ratio, an increased number of mitotic figures, including abnormal mitoses, nuclear hyperchromatism. (k, l) Signals were detected in the cell membranes and nuclei. (m-o) Signals were detected in the nucleus of the epithelial dysplastic cells (n) and carcinoma cells (o) in OSCC, but cell membranous expression was weak or absent. Scale bars: (a, b, d, e, g, h, j, k, m) 200 μm; (c, f, i, l, n, o) 50 μm.