Figure 2

Immunohistochemistry results targeting HPV-16 in tumor samples (cancer grade I-III). The positive expression of HPV-16, indicated by brown immunohistochemistry signals, located mainly in the cytoplasm of cancer cells. A, negative (-) in cancer grade I sample; B, slightly positive (±) in cancer grade II sample; C, positive (+) in cancer grade II sample; D, strongly positive (++) in cancer grade III sample. The brown staining was by DAB and the nuclei were slightly stained by haematoxylin (original magnification × 200).