Case report: Novel PIK3CA and AXIN1 mutations in acinar cell carcinoma of the stomach arising from pancreatic heterotopia

Acinar cell carcinoma (ACC) is a rare form of pancreatic cancer that has been reported to occur in pancreatic heterotopia of the gastrointestinal tract. Molecular profiling studies of primary pancreatic ACC describe genetic alterations distinct from pancreatic adenocarcinoma. However, molecular testing in ACC arising from pancreatic heterotopia has not been described. We report a case of ACC of the stomach associated with pancreatic heterotopia in a 76-year-old man. The clinical, microscopic, immunohistochemical, and molecular features are described, including analysis via a targeted 225-gene next-generation sequencing (NGS) panel. Two novel mutations involving PIK3CA and AXIN1 are described, with implications for therapeutic options. This study is the first to characterize the molecular profile of ACC arising in pancreatic heterotopia and broadens the molecular landscape of these rare tumors.