Epidermoid Cyst in an Intrapancreatic Accessory Spleen Complicating Clinical Decision-Making: A Case Report With Characteristic Imaging Findings.

Epidermoid cyst in intrapancreatic accessory spleen (ECIPAS) is a rare benign condition that occasionally mimic malignant pancreatic neoplasms. We present a case of ECIPAS in a 53-year-old asymptomatic male, initially discovered incidentally during imaging for a suspected hepatic hemangioma. The lesion, located in the pancreatic tail, demonstrated characteristic imaging features on contrast-enhanced computed tomography and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI), including a cystic component with peripheral solid tissue exhibiting splenic enhancement patterns. Despite these typical ECIPAS findings, the lesion increased in size from 38 × 33 mm to 50 × 45 mm over 12 months, accompanied by a significant rise in serum carbohydrate antigen 19-9 (CA19-9) from 21 to 330 U/mL. This clinical progression raised concerns about potential malignancy, leading to a robot-assisted spleen-preserving distal pancreatectomy. Histopathological examination confirmed the diagnosis of ECIPAS. Postoperatively, the patient's serum CA19-9 levels normalized. This case highlights that ECIPAS can complicate clinical decision-making through size increase and CA19-9 elevation, complicating preoperative diagnosis. However, careful analysis of imaging characteristics, particularly on SPIO-enhanced MRI, can aid in accurate diagnosis.