P928 - Primary Advanced Gallbladder Malignant Melanoma Successfully Eradicated With Immunotherapy and BRAF Inhibitors

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A 58-year-old male with past medical history significant for H. pylori positive gastric ulcer presented with pre-syncope. Physical examination revealed a vitally stable patient, with no jaundice or RUQ tenderness. CT pulmonary embolism protocol showed incidental biliary dilation and gallstones. Right upper quadrant US showed cholelithiasis and dilated CBD of 10 mm. Laboratory analysis revealed WBC=4.9bil/L, Hgb =13.5gm/dl, platelets=150k, ALP=322U/L, AST=178U/L, ALT=243U/L, TB=3.7U/L with direct portion=2.5U/L. ERCP was unsuccessful due to failure to canulate CBD. Laparoscopic cholecystectomy and open laparotomy were unsuccessful due to difficult resection. During laparotomy, firm fixed mass was found in gallbladder infundibulum and some fixed lymph nodes in the portal triad and hepatoduodenal ligament. Incisional biopsy with removal of stones and cholecystostomy were performed. MRCP showed intraluminal gallbladder heterogenous mass measuring 6 cm and multiple enlarged lymph nodes compressing the CBD. Microscopic pathology was consistent with malignant melanoma (image 1). Immunohistochemical stains were positive for S100, HMB-45 and SOX-10 (Image 2). CT chest, abdomen and pelvis, brain MRI and PET scan did not show evidence of other site involvement or metastasis. Ophthalmological examination was normal with no evidence of ocular melanoma. Dermatological evaluation was normal and random biopsies of skin nevi were negative for malignancy. He received nivolumab infusion then he was switched to debrafenib and trametinib. Most recent PET scan, body CT and MRCP showed good response to immunotherapy with no evidence of metastasis or active disease at 14 months follow-up visit. Later on, he underwent successful cholecystectomy, central hepatectomy, and portal lymphadenectomy. Microscopic pathology showed no evidence of melanoma and failure to stain with S-100 or SOX-10 in the entire resected specimen (image 3). The patient is stable at 8 weeks post-operative follow-up visit with no evidence of melanoma recurrence.

Primary gall bladder melanoma is a very rare type of melanoma. Some authors doubt its existence and believe it is secondary to occult primary melanoma elsewhere. Gall bladder is a relatively common site for melanoma metastasis. Treatment of melanoma is usually surgical. We believe this is the first case of advanced primary melanoma of the gallbladder, which was successfully treated and eradicated by immunotherapy and BRAF inhibitors.


American College of Gastroenterology (ACG) Annual Scientific Meeting, Orlando, FL, October 13-18, 2017.