S1601 Malignant Melanoma of the Gallbladder Masquerading as Cholangitis and Cholecystitis

Abstract

INTRODUCTION: Metastatic Malignant melanoma is reported in the stomach, intestine and colon. The involvement of the gallbladder and the bile duct are extremely rare. CASE DESCRIPTION/METHODS: A 61-year-old male presented with abdominal pain, nausea, vomiting, fever, chills, and 10lb weight loss. Physical examination was notable for right upper quadrant abdominal tenderness with a positive Murphy’s sign and minimal jaundice. Lab data showed no leukocytosis and normal hemoglobin. Elevated liver tests with Alk Phos 435U/L, ALT 546U/L, AST 474U/L, and Tbili 3.1mg/dl prompted an abdominal ultrasound which showed intrahepatic and extrahepatic bile duct dilatation (common bile duct (CBD) 11mm). A diffusely abnormal thick-walled gall bladder filled with debris was seen. This was concerning for cholecystitis and cholangitis. He was started on piperacillin/tazobactam. An endoscopic ultrasound (EUS) revealed hyperechoic material suggestive of thick sludge versus tissue within gallbladder lumen extending into the CBD (Figure 1a). Endoscopic retrograde cholangio-pancreatography (ERCP) revealed irregular filling defects within CBD close to cystic duct takeoff (Figure 1b). After sphincterotomy, balloon sweeps evacuated pigmented tissue debris (Figure 1c) which was retrieved and sent for pathology. Unusual EUS/ ERCP findings prompted an MRI which showed high T1 signal within periportal nodes and gallbladder suggesting hemorrhage. Surgical consultation was obtained and patient underwent laparoscopic cholecystectomy, but frozen section indicated malignancy, therefore, an open liver resection and lymphadenectomy was completed. The gross pathology showed a 2.5 × 1.6 × 1.5cm mass arising from the gallbladder (Figure 2a) with invasion into the peri muscular connective tissue on the hepatic side but with no direct extension. An immunostain on the tumor and the prior biliary tissue debris showed positive staining for Vimentin, and S100 and a diagnosis of melanoma was confirmed (Figures 2b and 2c). Surgical staging was pT2bN1. Skin and ocular examination did not reveal any lesions. DISCUSSION: Melanoma involving the gastrointestinal tract is usually metastatic from known cutaneous melanoma; however primary melanoma of the GI tract have been reported. Within the GI tract, primary gallbladder melanoma is extremely rare with less than 40 cases reported in the literature. Clinical course is typically aggressive; our patient developed metastatic disease to brain soon after gallbladder resection.Figure 1.: EUS and ERCP image.Figure 2.: Pathology image.