Figure 2. Morphological features and cytokeratin protein expression in SCC tissue. A and B: H&E staining of SCC tissue. A: Notice the thickening of the epithelium as demarcated by the white dotted line, the breach of the basement membrane and massive leukocytes infiltration (white arrows). B: The epithelial cell invasion of the stroma (marked by the dotted white lines). The keratin pearls formed by necrotic epithelial cells (white arrow). The invading cells showed typical metaplastic appearance with enlarged nucleus and cell volume. The original pictures were taken at 100× magnification. C and D: Immunofluorescent staining of cytokeratin proteins (green) in SCC tissue. C: CK14 antibody stained the full thickness of the epithelium. The signal was more intense along the basal cell layer. D: CK4 staining of the SCC epithelium except for the basal layer. E: Weak CK3/12 staining of the SCC epithelium. The nucleus was counter-stained blue with DAPI. The original pictures were taken at 200× magnification.