The differences between proctitis and rectal cancer are that under endoscopy, proctitis can present with patchy congestion, with or without mucus, and unclear vascular patterns. In contrast, rectal cancer can present with a protruding mass, which may have an uneven surface, cauliflower-like changes, and possibly congested erosion, among other conditions. It could also simply be a very superficial lesion, and the texture is often more brittle, possibly involving the entire circumference of the colon, preventing the passage of a colonoscope. Clinically, proctitis may present with symptoms such as increased frequency of bowel movements, incomplete evacuation, and sticky stools that may contain mucus. Rectal cancer, on the other hand, may present with symptoms such as bloody stools, positive fecal occult blood, abdominal pain, etc.