Multicystic Biliary Hamartoma of the Liver
A 52-year-old male patient was referred to our hospital on February 12, 2012 with a complaint of abdominal discomfort. The physical examination of the patient was unremarkable. The serum levels for alanine aminotransferase (21 IU/L; normal range, 5 to 35 IU/L) and aspartate aminotransferase (23 IU/L; normal range, 12 to 33 IU/L) were normal. Tumor markers (alpha-fetoprotein, carcinoembryonic antigen, and carbohydrate antigen 19-9) were within normal limits. Serological tests for hepatitis B and hepatitis C were negative. All other parameters were normal. An abdominal computed tomography (CT) scan demonstrated an irregularly-shaped low-density lesion measuring 2.7 cm in diameter in segment 3 of the left lobe just beneath the hepatic capsule (). This lesion was slightly enhanced after contrast medium injection and revealed a multicystic appearance in the portal phase (). Abdominal magnetic resonance imaging (MRI) more clearly depicted the multicystic nodule in segment 3 of the liver. On T2-weighted MRI, conglomerated multiple cystic nodules with a high signal intensity were seen (). Thin septae and the wall of the lesion were enhanced on contrast-enhanced, T1-weighted MRI (). Surgical exploration revealed a 2.7×2.0 cm, relatively well-demarcated nodular mass. The cut surface had a multicystic honeycomb appearance that was composed of a number of cystically dilated ductal structures embedded in the fibrous tissue (). Histologically, this lesion consisted of dilated cystic ducts, periductal glands and connective tissue, which included small amounts of hepatic parenchyma and blood vessels. Bile materials were observed in some of the cystic ducts (). The ducts were lined by a monolayer of low columnar or cuboidal epithelial cells (). There was no ovarian-like stroma. No mitotic figures were observed in the epithelial cells, and there was no evidence of pleomorphism or nuclear atypia suggesting malignant tumor. Immunohistochemical stainings for mucin core protein (Muc) 1, Muc2, Muc5Ac, Muc6, and biliary type keratin (K) 7 and, K19 were performed. Similar to previous findings,, the duct-lining epithelial cells were diffusely positive for K7, K19 and showed focal Muc1 expression, whereas they were negative for Muc2, Muc5Ac, and Muc6 (). On the basis of these histologic and immunohistochemical findings, a final diagnosis of MCBH was made.