Transitional polyps of the colon.

Fourteen polps with the gross appearance of small hyperplastic (metaplastic) polyps, not exceeding five mm in diameter, were removed from the rectum and the sigmoid colon of patients during colonscopy, and from surgical specimens. At light microscopy they were seen to be composed of apparently normal mucosa. In most cases some hyperplastic (metaplastic) and adenomatous polyps were also present. HID-AB stain revealed the polyps to be composed of "transitional" mucosa containing almost exclusively sialomucins, in contrast to normal mucosa, in which sulphomucins predominate. It is suggested that these "transitional" polyps may represent a reservoir of hyperplastic (metaplastic) and adenomatous polps, the different fate depending on different environmental situations.