S3471 Pancreatic Schwannoma: An Unexpected Cause of Peripancreatic Mass

Introduction: Among all pancreatic and peripancreatic tumors, pancreatic cancer is usually the most common cause. However, a number of other tumors, even with an indolent course can occur in the pancreas and its vicinity. In this case, we report a patient with a peripancreatic tumor of an unexpected etiology. Case Description/Methods: An 80-year-old man underwent an abdominal computed tomography scan for bilateral lower limb edema, which revealed an enlarged solid lesion adjacent to the uncinate process. A PET/computed tomography scan showed a 2.3 × 1.7 cm solid lesion medial to the uncinate process, suspicious for malignancy due to high metabolic activity. Serum CA 19-9 and CEA levels were undetectable. To further characterize the lesion, the patient underwent an endoscopic ultrasound, which showed a 2.4 × 2.0 cm well-defined peripancreatic hypoechoic lesion with a cystic component. Fine needle biopsy was performed, and histology showed positive staining for S-100 and SOX10, and negative staining for CD117, confirming the diagnosis of pancreatic schwannoma. The patient met with the surgery team, and the decision was conservative management given his age and comorbidities. Follow-up computed tomography scans at 3 and 12 months showed no morphological changes. Discussion: Pancreatic schwannomas are rare tumors, representing less than 1% of all schwannomas, and have a low risk of malignant transformation. Despite their benign nature, factors that may suggest potential malignancy include increasing tumor size and high mitotic activity (e.g., Ki-67). Computed tomography and magnetic resonance imaging cannot reliably distinguish benign from malignant lesions, whereas EUS with fine needle biopsy allows a more accurate diagnosis. Pancreatic schwannomas should be considered in the differential diagnosis of cystic pancreatic lesions. Although surgery remains the definitive treatment, conservative management with regular surveillance is a feasible and appropriate option in selected patients.