Although bronchogenic or esophageal duplication cysts are foregut-derived developmental anomalies most commonly encountered in the mediastinum and rarely in the abdomen, a cyst continuously extending into the abdomen via the esophageal hiatus has not been reported previously. We report a case of esophageal duplication cyst that occurred in the distal esophagus and extended continuously into the proximal portion of the stomach via the esophageal hiatus. A 62-year-old Japanese man was admitted to a local hospital complaining of dysphagia and upper abdominal pain. Abdominal ultrasound and CT scan revealed a cystic mass dorsal to the lateral segment of the liver that extended continuously into the mediastinum via the hiatus. The upper gastrointestinal series and endoscopic examination revealed extramural compression of the distal esophagus without mucosal lesions. Resection of the cystic lesion was performed by thoracotomy followed by laparotomy. The upper part of the cyst originated in the submucosal layer, extending into the muscularis propria of the distal esophagus. Histology of the resected specimen indicated that the cystic wall was composed of two smooth muscle layers and that the inner cystic wall was lined with pseudostratified columnar ciliated and/or squamous epithelium associated without cartilage or respiratory gland, indicating esophageal differentiation. These histological characteristics indicated that the cyst was an esophageal duplication cyst, rather than a bronchogenic cyst. This is the first case of a large esophageal duplication cyst of the distal esophagus continuously extending into the abdomen via the esophageal hiatus. The atypical location of this esophageal duplication cyst provides an insight into the pathogenesis of esophageal duplication cysts.
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