Ectopic respiratory mucosa in the rectum: the second documented case with discussion of its histogenesis.

Histopathological study of the endoscopically resected specimen revealed the presence of a unilocular cystic lesion under the rectal mucosa (Figure 1A). Smooth muscle bundles were recognized around the entire cyst (Figure 1A), and no connection with surface rectal mucosa was noted. The cyst wall was covered by pseudostratified ciliated epithelium (Figure 1B), and accumulation of neutrophils was observed within the cyst. The ciliated epithelium was without atypia, and no mitotic figures were observed. A few goblet cells were present. Mild lymphocytic infiltration and lymphoid follicle formation were also observed around the cyst (Figure 1A). No gastric, salivary, pancreatic, endometrial, and seromucinous gland tissues were present.