S3254 Metastatic Melanoma in the Pancreas Head: A Case Report

Introduction: Pancreatic adenocarcinoma is the most common primary pancreatic tumor; however, 2%–5% of pancreatic malignancies represent metastases, typically from the kidney, breast, lung, colon, with rarer origins including sarcomas or melanomas. Metastatic melanoma involving the pancreas is rare and diagnostically challenging due to nonspecific symptoms. We present a case of metastatic melanoma manifesting as a pancreatic head mass, highlighting the diagnostic process, management, and clinical course. Case Description/Methods: A 53-year-old man with metastatic melanoma to the lungs and kidney had been under oncology follow-up. His melanoma was diagnosed via kidney biopsy 1 year earlier, with no identifiable cutaneous primary. He underwent resection of left upper lobe lung mass confirming metastatic melanoma and received combination chemo and immunotherapy. He presented with pain, nausea, vomiting, and acute-on-chronic anemia. Lab work showed elevated liver enzymes and common bile duct (CBD) obstruction. Imaging Studies: A PET scan performed 1 week before admission showed a new hypermetabolic mass in the posterior pancreatic head. Computed tomography abdomen confirmed the pancreatic head mass with biliary obstruction. Biopsy and Histopathology: Endoscopic ultrasound-guided fine needle aspiration (FNA) of the mass revealed spindle and dyscohesive epithelioid cells with coarse brown pigment, consistent with metastatic melanoma. Endoscopic retrograde cholangiopancreatography (ERCP) identified a segmental biliary stricture; a sphincterotomy, papilla dilation, and temporary covered metal stent placement were performed. Discussion: Pancreatic metastases often present with nonspecific symptoms such as abdominal pain, jaundice, and weight loss. Imaging is crucial, with computed tomography and magnetic resonance imaging delineating tumor extent and Endoscopic ultrasound-FNA providing definitive diagnosis. Melanoma should be considered in patients with a suggestive history and pancreatic lesions. Treatment/Prognosis: Surgical resection was not feasible due to tumor location. Patient was restarted on combination immunotherapy (Opdualag), but follow-up PET showed no response. Advanced endoscopy revealed a jejunal melanoma lesion. Radiotherapy (25 Gy in 5 fractions) was delivered to pancreatic mass, and follow-up imaging showed treatment response. Conclusion: This case highlights the need to consider pancreatic metastasis in melanoma patients with new abdominal symptoms. While treatment options include immunotherapy, radiotherapy, and surgery, prognosis remains poor, with median survival of 6–12 months. Early recognition and histologic confirmation are vital for guiding management.