Beyond the abdomen: an unexpected finding of ectopic pancreas in a mediastinal mass.

Ectopic pancreas (EP) is a rare congenital anomaly defined as pancreatic tissue lacking anatomical or vascular continuity with the pancreas. Although it occurs in 0.25%-2% of the population, mediastinal EP is exceedingly rare, with fewer than 30 reported cases. We present a case of a 51-year-old woman found to have a large anterior mediastinal mass incidentally during trauma workup. Imaging revealed a cystic lesion with rim calcification, concerning for teratoma. Surgical resection via sternotomy was performed due to size and complexity. Histopathology demonstrated a duplication cyst containing pancreatic acini, ducts, and islets-confirming mediastinal EP. The patient remained asymptomatic postoperatively. This case highlights the diagnostic challenges of mediastinal EP, which often mimics other anterior mediastinal masses and typically requires surgical resection for definitive diagnosis. Recognition of EP, even in asymptomatic patients, is critical to guide management and prevent misdiagnosis of potentially benign lesions.