High-grade neuroendocrine carcinoma arising in a gastric duplication cyst: a case report with literature review.

Gastric duplication cysts are rare congenital anomalies that are mostly discovered in children but can remain asymptomatic and undetected into adulthood. Malignant transformation in gastric duplications is extremely rare, with most reported cases being adenocarcinomas. Herein, the authors report the first case of a high-grade neuroendocrine carcinoma arising in a gastric duplication cyst in a 40-year-old Asian male. This case highlights that duplication cysts should be included in the differential diagnosis of cystic masses of the gastrointestinal tract in adult, as well as pediatric, patients and emphasizes the importance of complete surgical resection and meticulous pathologic examination of these congenital anomalies.