Invasion of the rectum by carcinoma of the prostate.

Denonvillier's fascia ordinarily serves as an effective barrier to the posterior extension of carcinoma of the prostate. Consequently, it is generally unappreciated that cancer of the prostate can invade the rectum posteriorly and appear at diagnosis to be a rectal mass. Autopsy series show that this occurs in from 0.56% to 11.5% of all cases of prostatic carcinoma. When it does appear as a rectal mass, it can be confused with carcinoma of the rectum. Unless a biopsy confirms rectal carcinoma, such an error may even result in an inappropriate abdominoperineal resection of the rectum. Every surgeon must be aware of this entity, its presumed pathogenesis, and its three clinical types: rectal ulcer, stricture, and anterior rectal mass.