Pancreatic cancer mimicking ectopic pancreas origin: a rare case after neonatal pyloromyotomy.

Pyloromyotomy is a technique for relieving infantile hypertrophic pyloric stenosis and is performed almost safely without severe complications during long-term outcomes. To the best of our knowledge, this is the first reported case of pancreatic cancer arising from the pancreatic parenchyma embedded within the pyloric ring after neonatal pyloromyotomy. A 39-year-old woman with a history of infantile hypertrophic pyloric stenosis underwent a pyloromyotomy during the neonatal period and presented with progressive nausea and vomiting. Imaging studies suggested the presence of ectopic pancreatic or gastric cancer invading the pancreas. After laparotomy, tumor invasion of the pancreatic head was identified; therefore, pancreaticoduodenectomy was performed. Pathological examination confirmed pancreatic cancer arising from the pancreatic parenchyma embedded within the duodenal and pyloric muscle layers. The patient completed 6 months of adjuvant chemotherapy with oral S-1. Peritoneal dissemination was observed 23 months postoperatively. Abnormal embedding of the pancreatic head in the walls of the duodenum and pyloric ring was considered to be related to neonatal pyloromyotomy. This alteration requires careful preoperative evaluation and flexible surgical planning to achieve curative resection of atypical presentations of gastrointestinal malignancies. The cancer in the present case may be associated with long-term anatomical alterations following neonatal pyloromyotomy, although a direct causal relationship cannot be established.