Primary Malignant Melanoma of Bile Duct: A Rare Cause of Obstructive Jaundice: Presidential Poster

Abstract

Introduction: Malignant melanoma usually originates from squamous epithelium of skin, mucous membranes, retina, and uvea. Although melanoma can metastasize to any part of the body including biliary tract, primary malignant melanoma of bile duct (PMM-BD) is an extremely rare entity. Case presentaion: A 52 year-old gentleman with history of diabetes, multi-infarct dementia and polysubstance abuse presented with 5-month epigastric pain, with 1-week duration of jaundice, nausea/vomiting, pale stools and dark urine. He endorsed loss of appetite with 10-lb weight loss. Physical exam demonstrated scleral icterus and mild epigastric tenderness, and blood work suggested cholestatic jaundice (ALP 700IU/L, AST 86IU/L, ALT 96IU/L, bilirubin 20.9mg/dL). Abdominal CT showed large perihilar/peripancreatic mass involving portal vein and hepatic artery, thus deemed unsuitable for surgery. ERCP revealed intrahepatic biliary dilation with dilated common hepatic duct and mild narrowing of the common bile duct (CBD). After CBD brushing and biopsies, 8mm-6cm uncovered metal stent was placed for biliary decompression. Biliary brushings revealed neoplastic cells with eccentric/pleomorphic nuclei (Fig 1), strongly (+) for S-100 and MART (Fig 1). Extensive physical examination excluded any lesions suggestive of melanoma and patient denied any previously regressed/excised skin lesions. Whole body PET-scan showed spread to sub/supra-diaphragmatic lymph nodes and mesentery. Patient eventually succumbed to sequelae of brain metastases 3-months after the diagnosis.Figure 1Discussion: Majority of CBD melanomas are metastases from cutaneous sources and tend to be multiple, flat, pigmented lesions. On the contrary, PMM-BD is extremely rare (10 cases in literature only) and presents as single pedunculated polypoid mass in the lumen of duct. The diagnosis of melanoma is confirmed by immunohistochemical staining of tumor for S-100 & HMB-45 and additional electron microscopy. In our patient, lack of any prior history of melanoma including resected/regressed cutaneous lesions and lack of concurrent primary cutaneous/mucosal sites or other demonstrable metastases suggested it's primary nature. Treatment of choice for non-metastatic disease is pancreaticoduodenectomy with chemotherapy±radiation. Considering its rarity, it is difficult to ascertain the prognosis. Our case educates endoscopists about this rare entity, and also busts the myth that melanomas arise only from ectodermal derivatives.Table 1: Criteria for diagnosing it as primary