"Transitional" and hyperplastic-metaplastic mucosa occurring in solitary ulcer of the rectum.

Non-polypoid hyperplastic mucosa similar to that adjacent to colorectal carcinomas and adenomas, the so-called "transitional mucosa" (TM), was found in 16 out of 27 cases of solitary ulcer syndrome of the rectum. In 18 cases fully developed hyperplastic (metaplastic) mucosa was also found. It is suggested that chronic ischaemia which takes place in the solitary ulcer syndrome leads to TM as an exaggerated regenerative phenomenon. Later maturation of TM could lead to hyperplastic (metaplastic) changes.