Squamous Metaplasia in Colorectal Polyps

Naziheh Assarzadegan* and Felipe J. Solano

Squamous Metaplasia in Colorectal Polyps.

Two cases of colorectal polyps with foci of squamous metaplasia are reported. The first case showed a focus of squamous metaplasia arising within a tubular adenoma while in the
second case, the squamous metaplasia arose within a polyp with focus of intramucosal adenocarcinoma.

To the best of our knowledge there have been about 31 reports of squamous metaplasia in colonic adenomas documented in the literature since 1979.

We have encountered two additional cases of focal squamous metaplasia arising in a tubular adenoma of rectum and within and intramucosal adenocarcinoma of the sigmoid. To confirm the nature of these nests, immunohistochemistry was performed. In both cases the squamous nests were negative for
synaptophysin and chromogranin by immunohistochemistry.

Ki67 showed no staining in the area of metaplasia. Although it has been proposed that squamous metaplasia may serve as the precursor lesion in colorectal squamous neoplasms, the importance and significance of squamous metaplasia in colorectal polyps remain to be determined.

Metaplasia is defined as a reversible adaptive change in which one differentiated cells type is replaced by another cell type that is better able to tolerate the adverse environment.

Squamous metaplasia is the most common type of epithelial metaplasia. Epithelial metaplasia is a two edge sword and in most circumstances represents an undesirable change.

In addition, the persistent predisposing influences to metaplasia may initiate malignant transformation in metaplastic epithelium. Squamous metaplasia has been rarely reported in neoplastic and non-neoplastic large bowel.

The histogenesis and etiology of squamous metaplasia in colorectal adenomas is unclear, however chronic inflammation and mucosal irritation have been suggested as possible associations.

Some authors have also suggested the possibility of derivation from foci of squamous metaplasia
associated with chronic mucosal irritation.

Pathol Lab Med Open J. 2015; 1(1): 1-2. doi: 10.17140/PLMOJ-1-101