Figure 1.

Scoring of Ki-67 immunostaining. Representative examples are shown for the three-tiered score system of Ki-67 immunostaining. Nuclear Ki-67 staining in cells of the squamous epithelium is scored positive. Positive nuclei in the basal layer is considered a normal staining pattern and scored as 0 (A), positive nuclei predominantly found in the lower one-third of the epithelium as 1 (B), positive nuclei predominantly found in lower two-thirds of epithelium as 2 (C), and positive nuclei in more than two-thirds of epithelium as 3 (D). An example of individual scattered positive cells found in the upper layers of the epithelium in a predominant parabasal staining pattern is shown (E).