Activated Checkpoint Kinase 2 Expression and Risk for Oral Squamous Cell Carcinoma

Photomicrographs of representative pChk2 immunostaining. A. Nuclear staining (brown) of the surface epithelium demonstrating considerable variation in the intensity of the stain within a given field. A diffuse staining pattern is observed (as opposed to sporadic and scattered positivity) involving full thickness of the epithelium. Magnification, ×100. B. A mitotic figure staining dark brown +3 intensity (short arrow), the golden brown staining (two arrowheads) is of +2 intensity, the lighter but discernable brown staining (two longer arrows) is of +1 intensity, and the faint brownish color (circle) was considered as background staining. A complete absence of brown stain (rectangle) was interpreted as negative staining. Magnification, ×400. The fraction of cells exhibiting nuclear staining of various intensity (0, +1, +2, and +3) was estimated and added together to formulate the cumulative score. For example, in the field shown ∼1% has +3 intensity, 15% with +2, and 30% with +1 intensity, which will yield (1% × 3) + (15% × 2) + (30% × 1) = 0.63 cumulative score. Each slide was independently reviewed thrice and then the results between two pathologists compared to assure consistency.