Colloid-empty follicles, tubular or elongated, were lined by pseudostratified tall, columnar cells with clear cytoplasm.

Cell elongation changes cuboidal cells into columnar cells, and apical constriction then causes them to adopt apically narrow, wedge-like shapes.

These results suggest that endometriosis may originate from the columnar cells with ERs and PRs in the pelvic peritoneal lining.

Non-neoplastic control colon showed carbonic anhydrase I and II in the cytoplasm of the columnar cells lining the upper half of the crypts.

Columnar cells and occasional glandular structures were also seen.