A 54-year-old man comes to the office due to increasing pain in the right upper quadrant, nausea, and unintentional weight loss. Vitals signs are within normal limits. BMI is 21 kg/m². The patient appears cachectic and there is scleral icterus. The liver is palpable 3 cm below the right costal margin. No ascites is present. Laboratory studies reveal elevated bilirubin and alkaline phosphatase. Contrast CT scan of the abdomen demonstrates moderately dilated right and left intrahepatic bile ducts, with a vague area of delayed enhancement at their convergence. Biopsy of the lesion reveals columnar cells with hyperchromatic oval nuclei with prominent nucleoli arranged in glandular structures; mucin production with surrounding desmoplastic reaction is present. Which of the following is the most likely diagnosis?

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11ec160b_3931_d138_9249_8bc1014f671b_MD0001_00 This patient with weight loss, pain in the right upper quadrant (RUQ), and jaundice has radiographic and histologic findings consistent with cholangiocarcinoma, a malignancy of the bile duct epithelium. It is associated with primary sclerosing cholangitis; however, it may occur sporadically. Cholangiocarcinoma is often clinically silent until late in the disease course, when the tumor obstructs bile drainage, leading to a characteristic cholestatic pattern of liver injury (elevated alkaline phosphatase, hyperbilirubinemia). Progressive weight loss, RUQ pain, jaundice, and hepatomegaly are typical, and occasionally, the gallbladder is palpable (Courvoisier sign). Intraductal malignancies are often difficult to visualize radiographically but usually demonstrates dilated bile ducts in the absence of an obstructing gallstone. The most frequently involved site is at the confluence of the right and left hepatic bile ducts (Klatskin tumors), which may be visible as nonunion of the bile ducts (as in this patient). Most cholangiocarcinomas are adenocarcinomas characterized histologically by columnar epithelial cells with prominent nucleoli arranged in glandular structures with mucin production and significant desmoplasia (reactive fibrous tissue surrounding a malignant mass). (Choice B) Focal nodular hyperplasia is a benign, nonencapsulated liver tumor that typically occurs in women. It is characterized by fibrous septa encasing normal hepatocytes and a central stellate scar, which is visible both histologically and radiographically. (Choice C) Hepatic adenomas are benign lesions that develop most commonly in women taking oral contraceptives. Jaundice and weight loss are unexpected, and an abdominal CT scan usually demonstrates a solitary lesion in the hepatic parenchyma, not the biliary tree. Histology reveals relatively uniform hepatocytes arranged in thin cell plates without atypia. (Choice D) Hepatocellular carcinoma is a malignant liver mass that most often develops in patients with cirrhosis. Microscopy demonstrates polygonal cells with abundant eosinophilic cytoplasm and prominent nucleoli. (Choice E) Metastatic colon cancer is characterized by adenocarcinoma with gland formation; however, it usually causes multiple hepatic masses, which are not seen on this patient's CT scan. In addition, the location of the mass at the bifurcation of the common hepatic duct is characteristic of cholangiocarcinoma. Educational objective: Cholangiocarcinoma is a malignancy of the bile duct epithelium that eventually obstructs biliary drainage, resulting in cholestasis (elevated alkaline phosphatase, hyperbilirubinemia) with jaundice, weight loss, pain in the right upper quadrant, and hepatomegaly. Imaging often demonstrates dilated bile ducts in the absence of an obstructive gallstone, and biopsy reveals an adenocarcinoma with columnar cells, mucin production, and a significant desmoplastic reaction. __________ References: Intrahepatic cholangiocarcinomas have histologically and immunophenotypically distinct small and large duct patterns. (http://www.ncbi.nlm.nih.gov/pubmed/30001234)

A 54-Year-Old Man Comes to the Office Due to Increasing