S5451 A Rare Case of Metastatic Melanoma to Porta Hepatis: A Case Study

Introduction: Metastatic melanoma, particularly with unusual presentations such as obstructive jaundice due to porta hepatis involvement, brings on significant diagnostic challenges. While melanoma commonly spreads to the liver, isolated involvement of the porta hepatis is exceedingly rare and can be mistaken for lymphoma or other malignancies. This necessitates a high index of suspicion and reliance on advanced diagnostic procedures such as endoscopic ultrasound (EUS) with fine-needle aspiration (FNA) for accurate diagnosis and targeted therapy. Case Description/Methods: A 64-year-old man with bipolar disorder (on lithium) presented with 4 weeks of progressive lower abdominal pain, weight loss, and obstructive jaundice. Initial imaging using computed tomography (CT) scan and magnetic resonance cholangiopancreatography revealed multilobulated porta hepatis masses, peripancreatic lesions, and biliary dilation, concerning for metastatic disease versus lymphoma. EUS-guided biopsy of a porta hepatis lymph node confirmed metastatic melanoma (BRAF V600E+) despite no identifiable cutaneous primary lesions. A month after diagnosis, the patient had an episode of clinical deterioration marked by worsening cholestasis (bilirubin 5.6 mg/dL, alanine aminotransferase 808 U/L, aspartate aminotransferase 328 U/L) and malignant biliary obstruction secondary to the metastatic cancer as noted on repeat CT abdomen and pelvis which prompted endoscopic retrograde cholangiopancreatography (ERCP) with dual stenting: a 10 mm partially covered metal stent relieved a mid-common bile duct stricture, while a 7 Fr pigtail stent in a low-insertion cystic duct was placed for cholecystitis prevention. Post-procedural LFTs improved significantly (bilirubin 1.6 mg/dL at discharge). Immunotherapy with opdualag was promptly started prior to hospitalization and tumor regression response was confirmed 2 months after initiation with positron emission tomography scan, though persistent abdominal pain necessitated palliative care coordination. Discussion: The occurrence of metastatic melanoma presenting with obstructive jaundice and involving the porta hepatis is rare, with only a handful of cases reporting metastasis to the liver rather than isolated porta hepatis as with our patient. Melanoma is usually derived from cutaneous primaries; however, it can have atypical metastatic patterns, which complicates diagnosis. In this context, distinguishing between lymphoma and metastatic melanoma based solely on initial imaging findings may lead to a poor outcome. Our case aims to present a unique case of obstructive jaundice and its diagnostic complexities.