Hepatobiliary and pancreatic: Alveolar echinococcosis mimicking hepatocellular carcinoma

Human alveolar echinococcosis is a rare disease caused by Echinococcus multilocularis. The disease is restricted to the northern hemisphere and most cases have been described in central Europe, Canada, China and Japan. The most common definitive and intermediate hosts are foxes and voles, respectively. Human infections can be acquired by exposure to parasite ova in the feces of infected foxes or dogs. In the liver, the larval mass remains in the proliferative phase indefinitely with invasion and destruction of normal tissue. There are also reports of metastatic spread, occasionally to the lungs or brain. Macroscopically, larger lesions have a central cavity containing turbid, brown fluid surrounded by pale tissue that lacks a clearly-defined border. The diagnosis of alveolar echinococcosis is usually made by imaging and serological studies. One helpful imaging feature is that of marginal calcification. However, the differential diagnosis can include various hepatic tumors including hepatocellular carcinoma. Suspicion of alveolar echinococcosis is normally considered a relative or absolute contraindication for liver biopsy. However, in the case illustrated below, a biopsy was performed as the clinical setting seemed to favour the diagnosis of hepatocellular carcinoma. A 27-year-old man was admitted to hospital with jaundice, dark urine and pruritis. He did not describe significant abdominal pain but had noted weight loss of 4 kg over the preceding 4 months. He was known to have hepatitis C, presumably acquired by use of intravenous drugs. On physical examination, he was tender over the right upper quadrant of his abdomen. Blood tests revealed an elevated serum bilirubin and liver enzymes but his alpha-fetoprotein level was within the reference range. An abdominal computed tomography (CT) scan showed a large mass, 16 × 13 × 14 cm in size, that occupied most of the right lobe of the liver. The mass showed central necrosis, irregular margins and patchy calcification in peripheral areas (Figure 1). Two liver biopsies were taken under CT guidance; the first only showed necrotic tissue but the second showed laminated membrane with vesiculo-tubular structures that were highlighted by a periodic acid-Schiff stain (Figure 2, original magnification ×100). The diagnosis of E. multilocularis infection was supported by strongly positive serological tests using crude and recombinant parasite antigens. Contributed by

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