Heterogeneity of pancreatic neoplasms arising in pancreatic heterotopia: a single institution review.

Pancreatic heterotopia (PH) is a well-characterized entity that can arise in the gastrointestinal tract. Many pancreatic disease processes, ranging from inflammatory to neoplastic, can also be seen in PH. Neoplastic transformation in PH remains exceedingly rare. A retrospective review of PH cases (1990 to 2020) excised at our institution was performed. Cases were selected based on prior criteria for identifying neoplastic transformation in PH. Clinical information was obtained through the electronic medical record. A total of 163 gastrointestinal tract PH cases were identified. Of these, seven had a neoplastic process in the heterotopic pancreas: two with well-differentiated neuroendocrine tumors, three with pancreatic intraepithelial neoplasia, and one each developed ductal adenocarcinoma or neuroendocrine microadenoma. The majority were men (71.4%) with a median age of 64 years. Seven patients had clinical symptoms including weight loss, abdominal pain, and small bowel obstruction. Five cases arose in the small intestine and two cases arose in the stomach. Lesions involved the submucosa (42.8%), serosa (28.6%), and muscularis propria (28.6%). In all cases, the PH was composed of acini, ducts, and islet cells. The mean follow-up time was 55 months (range: 3-159 months). One patient had regional lymph node metastasis and died with disease from surgical complications. No cases of distant metastasis were identified. Neoplasia in PH is a rare phenomenon that can occur, including malignant entities such as ductal adenocarcinoma, but also other tumor types. Recognition of this entity remains important for pathologists to avoid diagnostic confusion and provide accurate tumor staging.