Cytokeratins 7 and 20 and mucin core protein expression in esophageal cervical inlet patch

Cervical inlet patch (CIP) is defined by the presence of gastric mucosa within the first few centimeters of the esophagus. Several endoscopic series have demonstrated a frequent association of CIP with Barrett's esophagus (BE) suggesting a pathogenetic link. A histochemical study reporting the presence of acid mucin in CIP, including sulfomucin, supports this hypothesis. We evaluated mucin core protein expression and cytokeratins 7 and 20 (CK7/CK20) pattern in biopsies of CIP, normal antrum, and BE to comment on a possible relationship of CIP with BE. We observed that both lesions have similar cytokeratin patterns with mixed CK7/CK20 reactivity on the surface and pits and lone CK7 positivity in the glands. MUC5AC was strongly expressed on the surface and pits but not in the glands of CIP and antral mucosa. Within BE, MUC5AC positivity was noted not only on the surface and pits but also in the glands. MUC6 similarly decorated the glands of CIP and BE. MUC2 was expressed rarely in CIP with goblet cells but conspicuously on the surface and pits of BE. MUC5B was seen in both CIP and BE and rarely in the antral mucosa. The similarities between CIP and BE but not with normal antral mucosa fits with the hypothesis that both lesions may originate from submucosal esophageal mucous glands. Two pathogenetic pathways can be entertained: focal upper esophageal mucosal misdevelopment in pediatric population and patchy metaplastic replacement of squamous mucosa in adults with gastroesophageal reflux disease.