Cystic Lesion Mimicking Intraductal Papillary Mucinous Tumor Arising in Heterotopic Pancreas of the Stomach and Synchronous Intraductal Papillary Mucinous Adenocarcinoma of the Pancreas

This article presents the study of a 66-year-old man with an asymptomatic pancreatic mass detected incidentally 4 months earlier. A magnetic resonance imaging scan revealed 2 distinct cystic masses in the pancreas and the gastric antrum. Microscopically, the pancreatic lesion showed dilated cysts containing papillary structures lined by mucinous epithelium, which showed a loss of polarity, an increased nucleus-to-cytoplasm ratio, a prominent nucleolus, and high proliferation on immunostaining for Ki-67. The gastric lesion was composed of heterotopic pancreatic tissue surrounding a large dilated cyst that was lined with mucinous epithelium and contained a few intraluminal papillae.