Fig. 3

Findings of the second anal canal tumor. a Endoscopic appearance. b Histological appearance of a low magnification (original magnification: 40 ×). The border between adenoma and normal epithelium is indicated by an arrowhead. Bar indicates 1 mm. The inset shows a higher-magnification view (original magnification: 200 ×). c Immunohistochemical staining of p16 in the second anal canal tumor (original magnification: 200 ×). Only 4 % of tumor cells were positive for p16. Bar indicates 100 μm