Detection of Anal Intraepithelial Neoplasia and Anal Squamous Cell Carcinoma on Colonoscopy

The purpose of this case series is to review the endoscopic detection of anal intraepithelial neoplasia and anal squamous cell carcinoma including the role of rectal retroflexion and narrow-band imaging. Four cases of anal intraepithelial neoplasia were incidentally discovered in women aged 55-71 years. Anal lesions identified included sessile polyps, nodular mucosa, and circumferential polyps. A fifth patient, who presented with abdominal pain, was found to have a 3 cm anal squamous cell carcinoma on diagnostic colonoscopy, despite a negative colonoscopy 21 months earlier. In the absence of contraindications, retroflexion should be performed on all patients. Suspicious anal mucosa warrants biopsy.