Opisthorchiasis and cholangiocarcinoma — DTM&H MCQ
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Correct answer: D — Cholangiocarcinoma
The correct answer is D, cholangiocarcinoma. The stem describes a classic Southeast Asian exposure history: raw freshwater fish consumption in Laos, recurrent cholangitis, and ERCP findings of biliary stricture with periductal fibrosis, which together are the hallmark of chronic liver fluke infection (Opisthorchis viverrini or Clonorchis sinensis). These flukes live in the intrahepatic and extrahepatic bile ducts, causing chronic inflammation, periductal fibrosis, and epithelial hyperplasia that progress over years to cholangiocarcinoma. Opisthorchis viverrini and Clonorchis sinensis are classified by IARC as definite (Group 1) biological carcinogens specifically for their causal link to cholangiocarcinoma, and the Mekong basin (Laos, Thailand, Cambodia) has the highest global incidence of this cancer as a direct consequence. Why the other options are wrong: A. Hepatocellular carcinoma: This arises from hepatocyte injury, classically from chronic hepatitis B or C infection, cirrhosis, or aflatoxin exposure, not from biliary tract fluke infestation, which targets the ductal epithelium rather than the liver parenchyma. E. Colorectal carcinoma: There is no established causal pathway between hepatobiliary fluke infection and colonic epithelial malignancy; risk factors for colorectal cancer relate to diet, inflammatory bowel disease, and inherited polyposis syndromes. C. Gallbladder carcinoma: Although flukes can inhabit the gallbladder, the dominant and strongly evidenced malignant sequela of chronic opisthorchiasis and clonorchiasis is bile duct (not gallbladder) carcinoma; gallbladder cancer is more typically linked to gallstones and porcelain gallbladder. B. Pancreatic adenocarcinoma: This is driven by smoking, chronic pancreatitis, and genetic factors; periductal biliary fibrosis from fluke infection does not have a recognised causal association with pancreatic ductal malignancy. Key point: Recurrent cholangitis with periductal biliary fibrosis after raw freshwater fish ingestion in the Mekong region points to chronic liver fluke infection, the leading cause of cholangiocarcinoma worldwide.
Reference: IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 100B: Biological Agents (Opisthorchis viverrini and Clonorchis sinensis), International Agency for Research on Cancer, WHO, https://publications.iarc.fr/120