Peptic ulceration occurs at all the following sites except -
Peptic ulcer

Ulcers are defined histologically as a breach in the mucosa of the alimentary tract that extends through the muscular mucosa into the submucosa or deep.
Peptic ulcers are chronic, most often solitary lesions that occur in any portion of the gastrointestinal tract exposed to the aggressive action of acid/peptic juice.

Peptic ulcers located in the following sites, in order of decreasing frequency :

Duodenum, 1st portion
Stomach, usually antrum
At the gastro - esophageal junction in the setting of gastroesophageal reflux or Barrett's esophagus.
Within the margins of a gastrojejunostomy.
In the duodenum, stomach or jejunum of patients with Zollinger -Ellison Syndrome.
Within or adjacent to Meckel's diverticulum that contains ectopic gastric mucosa.
Lesser curvature
First part of duodenum
Lower end of esophagus
Stoma of gastric portion of gastrojejunostomy