I've had a negative colonoscopy and prostate/rectal sonogram, do they both detect anal cancer? Is anal cancer common?

Anal cancer. can be detected by direct rectal exam or anoscopy, without colonoscopy. Trananal prostate ultrasound does not detect anal cancer. Anal cancer is less common than colorectal cancer. If digital exam and colonoscopy are both negative, it is unlikely that you have anal cancer.
Not common. Anal cancer is squamous in origin and below field seen with colonoscopy. Best detected digitally and its depth into muscles by sonography. After bx confirming path, treatment is RT and mitocycin C.